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DIDEROT'S EARLY 
PHILOSOPHICAL WORKS 




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The Open Court Series of C/tissics of Science and 
'Philosophy^ .7\(o, 4 

DIDEROT'S EARLY 
PHILOSOPHICAL WORKS 



TRANSLATED AND EDITED BY 

MARGARET JOURDAIN 






1' <,« 



i 







CHICAGO AND LONDON 
TME OPEN COURT PUBLISHING COMl'ANV 

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XVIZ 



Copyright in Great Britain under the Act of \f)\\ 



TABLE OF CONTENTS 

PAGE 

Introduction i 

Philosophic Thoughts 27 

Letter on the Blind ...... 68 

Addition to the Letter on the Blind . . 142 
Letter on the Deaf and Dumb . . . 158 
Notes . . . . . . . . .219 

Appendix . . . . ■ . . .226 

Index ......... 245 



DIDEROT'S EARLY 
PHILOSOPHICAL WORKS 

INTRODUCTION 

Diderot 

A COMPLETE survey of the life and works of Diderot 
— whom Voltaire called Pantophile — is not attempted 
here, for the list of the topics he handled would be 
a very long one, including as it does various depart- 
ments of art and science and speculation. The 
Letter on the Blind (the most interesting of his 
early works), however, shows him in two lights — 
as a free-thinker and as one of the long succession 
of thinkers who prepared the way for the theory of; 
evolution. The agitation caused by Diderot and 
his circle about the theory of transformism, it has 
been said, must have largely contributed to awaken 
the attention of Erasmus Darwin in England and 
Lamarck in France to the necessity of throwing 
more positive light on that great issue. Transformism 
only needed the partial scientific confirmation which 
Lamarck and Geoffroy St Ililairc gave it in the first 
two decades of the nineteenth century to pass from 
the realm of systematic philosophy into that of 

I 



2 DIDEROT S PHILOSOPHICAL WORKS 

scientific controversy. Lamarck, who was for some 
time the protege of Bufifon, and in 1785 became a 
contributor to the Methodic Encyclopcedia ^ (edited 
by Naigeon and other friends of Diderot), eventu- 
ally founded transformism when he subjected it to 
definite laws.^ Throughout the Letter on the Blind, 
>knd indeed throughout Diderot's work, is apparent 
'his indebtedness to En g l ish tho ught ; then, and in 
later life, he was the mjst English of Frenchmen — 
the man who could write to Catherine II. in 1775 
that "it is obvious to all who have eyes in their 
head, that if it had not been for the English, reason 
and philosophy would be still in the most pitiable 
and rudimentary condition in France." In Brune- 
tiere's words, " There is no trace of anything but 
England in the work of the man who has often been 
described as the most German of Frenchmen."^ 

Denis Diderot was born at Langres on October 5 th, 
171 3. He was educated by the Jesuits, and threw 
himself into the Bohemian life of a bookseller's hack 
in Paris. His earl}- writings were mere hackwork 
— a translation of Stan}'an's History of Greece (1743), 
for which he earned lOO crowns, and a translation 
(with two collaborators) of James's Dictionary of 
Medicine ( 1 746-48). The rendering of Shaftesbury's 
Inquiry concerning Virtue and Merit (1745) has 
some notes of his own. Besides his volume of 
stories. The Indiscreet J eivels (1748), he wrote the 

^ Encyclopidie JlMkodtque. 

^ R. L. Cm, Diderot and English Thought, New York, 1913. 
^ F. Brunetiere, Manuel de Fhistoire de la litt^rature francaise, 
1898, p. 321. 



INTRODUCTION 3 

Philosophic Thoughts and TJie Sceptic's Walk 
(1747) — an allegory pointing to the extravagances 
of Catholicism and the uncertainty of philosophy. 
For his Letter on the Blind he was imprisoned, at 
Vincennes. In a second piece, published after the 
Letter on the Blind, Diderot considered the case of 
the deaf and dumb. The Letter on the Deaf and 
Dumb, however, is an , examination on some points 
in aesthetics, not a fragmen*^ of scientific speculation 
like the earlier Letter. 

On his release from imprisonment at Vincennes, 
at the instance of his bookseller he entered upon his 
life work, the Encyclopcedia. In 1745 a bookseller, 
Le Breton, suggested to Diderot a book that should 
be all books. In 1750 appeared d'Alembert's pre- 
face, and the first volume appeared in 175 1. For 
years the history of Diderot and the Encyclopczdia 
was the same thing. " The thing will surely pro- 1 
duce a great revolution in the human mind," he said ' 
of it ; "we shall have served humanity." 

Diderot, who was not equal to the task of super- 
vising every department of this gigantic enterprise, 
associated with himself as colleague d'Alembert, to 
whom he turned for aid in the mathematical articles. 
D'Alembert withdrew from the venture in 1758, 
worn out with affronts and vexations of every kind ; 
and for seven years the labour of carrying the vast 
work to its close fell upon Diderot alone. Besides 
his labours as editor, he contributed articles on a 
vast scale, so that his contributions fill more than 
four of the volumes of his collected works. The 



4 DIDEROT'S PHILOSOPHICAL WORKS 

EncyclopcBdia, from the spirit in which it was written, 
became not merely a dictionary, but a party — the 
school of destruction, the Trojan horse introduced 
within the walls of the old regime, and the Revolu- 
tion in being. 

In 1754 he wrote Thoughts on the Interpretation 
of Nature — a series of aphorisms upon science and 
the problem of man's knowledge of the universe as 
a whole ; and in 1769, three dialogues, the first 
between himself and d'Alembert ; the second, d'Alein- 
berfs Dream, in which the dreaming d'Alembert 
continues the discussion ; and a third and final 
discussion between the physician Bordeu and 
Mademoiselle de I'Espinasse. While in the 
Thoughts on the Interpretation of Nature he was 
'not fully in sympathy with the materialistic thesis, 
in d'Alemberfs Dream he figures definitely as a 
materialist. 

Besides his scientific and speculative works, Diderot 
found time for writing plays in the sentimental vein 
{The Natural Son and Father of a Family), for art 
criticism (the Salons), and for sketches and mis- 
cellaneous pieces such as Rameau's Nephew. 

A Parisian of the Parisians, Diderot made one 
foreign tour to Russia and Holland, and passed 
some months in St Petersburg. He returned home 
in 1774. He died on July 30th, 1784. 

^ ^Philosophic Thoughts 
The Philosophic Thoughts are said to have been 
thrown together between Good P"riday and Easter 



INTRODUCTION 5 

Sunday of 1746. They were ordered by the 
Parliament of Paris to be burnt, with some other 
books (July 7th). The edition of 1746, however, 
is not rare, and the Philosophic Thoughts were re- 
printed in France, and translated into German and 
Italian. They were frequently attacked and criti- 
cised ; among the hostile critiques being : Pensces 
philosophiques et pansees chretiennes mises en paraT 
lele, La Haye, 1746 ; Pensees raisonnables oppose es 
aux Pensees philosophiques, by Formey, Berlin 
(Amsterdam), 1749 ; Pensees philosophiques dun 
citoyen de Montmartre, by Senemaud, 1756 ; Pensees 
philosophiques sur divers sujets, La Haye, 1761 ; 
and Lettres sur Vecrit intitule Pensees philosophiques 
et sur le livre des Mceurs, 1749. 

Diderot's little book was among those found in 
the possession of La Barre, 

In the Philosophic Thoughts Diderot still figures 
as a Deist, opposing his God to the God of Pietists 
and reading a lesson to the atheist (Thoughts XXII 
and XXIII). In Thought LVIII he proffers a con- 
fession of faith in "the Roman, Catholic, and 
Apostolic Church " which evidently did not disarm 
his judges. 

This and other references to Christianity are 
'* no more than ironical deference to established 
prejudices " (Morley, Diderot, vol. i, p. 48). As 
d'Alembert wrote of the Encyclopcedia, " Time will 
enable people to distinguish what we have thought 
from what we have said." 

In Thought XX Diderot adduces the argument 



6 DIDEROT S PHILOSOPHICAL WORKS 

from design as a proof of the existence of a God. 
In The Sceptic's Walk, however {CEuvres, i, p. 229), 
his atheist puts the case against design as a proof of 
the existence of God very trenchantly, and in the 
Letter on the Blind {ibid., p. 311) Saunderson also 
makes an eloquent protest against the inadequacy of 
this proof. 

The Letter on the Blind 

^ The Letter on the Blind is described in the Encyclo- 
pcsdia ^ as a very subtle metaphysical work, contain- 
ing certain passages which may offend pious ears. 
This estimate still may stand to-day. The interest 
of the letter is twofold : firstly, the scientific dis- 
cussion, where he treats of the theory of vision, 
and of how far a modification of the senses 
would involve "a modification of the ordinary 
notions acquired by men who are normally en- 
dowed in their capacity for sensation " ; - secondly, 
the argument that the argument from design is 
very weak evidence for both blind and sighted 
men. 

The Letter is, as it claims, a discursive and 
familiar docum.ent rather than a scientific treatise ; 
and, written as it was to fill the purse of Madame 
de Puisieux, the writer of some forgotten literary 
pieces and with some pretensions to bel esprit, her 
shadow often falls across its pages. Diderot broke 

^ Art. Aveugle ; see Appendix I. 

- John Morley, Diderot and the Encyclopedists, London, 1886, 
vol. i, pp. 85-86. 



INTRODUCTION i5 

has been worked up into many apologues and fables 
since that it has fallen into the domain of familiar 
things ; but it has its importance as one of the many 
saps in the direction of the strongly entrenched 
forces of Catholicism. 

Nicholas Saunderson 

The Nicholas Saunderson who figures in the 
Letter on the Blind is treated with respect for 
historical truth as far as his life and attainments are 
concerned, but, as is well known, in his dying speech 
he is merely the mouthpiece of Diderot. Saunder- 
son was born in January 1682 at I'hurleston, in 
Yorkshire, the son of an exciseman, and lost his 
sight at the age of twelve months by small-pox ; so 
that he can be classed among those persons blind 
from birth or from early infancy, whose case Diderot 
discusses. He became a good Latin, Greek, and 
French scholar, and after leaving school studied 
mathematics at home until 1707. He was then 
brought to Cambridge by Joshua Dunn, a fellow- 
Commoner of Christ's College, with whom he lodged. 
With the consent of William Whiston, Lucasian 
professor, he lectured to a class on the philosophy of 
'Newton, hydrostatics, mechanics, sound, astronomy, 
and optics ; and after the expulsion of Whiston from 
the professorship in 17 10, Saunderson was chosen 
on Tuesday, November 20thT* 171 1, as his successor, 
in spite of some opposition.^ Newton, however, 
interested himself very much in the election. His 

' Reid, Diary, 1709-1720, ed. Luard 1S60. 



1 6 DIDEROT'S PHILOSOPHICAL WORKS 

inauguration speech was delivered in very elegant 
Latin and "a style truly Ciceronian." He resided 
at Christ's College until 1723, when he took a house 
at Cambridge. He spent seven or eight hours a day 
in teaching, and some of his lectures are preserved 
in MS. at the University Library. He married a 
daughter of William Dickons, rector of Boxworth, 
by whom he had a son and a daughter. He died of 
scurvy on April 19th, 1739, and was buried at Box- 
worth, where there is a monument to his memory. 
There is a portrait of him, holding an armillary 
sphere, in the University Library, and an engraving 
by Vandergucht is prefixed to the edition of his 
Algebra, published by subscription in 1740. 

Lord Chesterfield, who attended Saunderson's 
lectures when at Trinity Hall, speaks of him as a 
professor who had not the use of his own eyes but 
taught others to use theirs. Like many other blind 
persons, his sense of touch and his hearing were 
extremely delicate. " He could judge of the size 
of a room into which he was introduced by the 
distance he was from the wall : and if ever he had 
walked over a pavement in courts, piazzas, etc., 
which reflected a sound, and was afterwards con- 
ducted thither again, he could exactly tell where- 
abouts in the walk he was placed, merely by the 
note it sounded."^ He was a good performer on 
the flute, and could distinguish to the fifth part of 
a note. He distinguished, in a set of Roman 

^ Memoirs of the Life and Character of Dr Nicholas Saunderson, 
in Saunderson's Algebra (ed. 1740), vol. i, p. 13. 



INTRODUCTION 17 

medals, the genuine from the false, " though they had 
been counterfeited with such exactness as to deceive a 
connoisseur who had judged by the eye." But, says 
the writer of the memoir, "I, who had not that 
sense to trust to,^ could easily feel a roughness on 
the new cast, sufficient to distinguish them by." 

Saunderson, who became a Fellow of the Royal 
Society in 17 19, and was acquainted with de Moivre, 
Machin, and Keill, was a devout Newtonian. His 
Algebra, prepared during the last six years of his 
life, was published in 1740 by his widow and daughter. 
Some of his manuscripts were printed in 175 1, with 
the title The Method of Fluxions applied to a Select 
Number of Useful Problems, together with the 
Demonstration of Mr Cotes' s forms of Fluents in 
the second part of his Logometria, the Analysis of the 
Problems in his Scholimn Generale, and an Explana- 
tion of the Principal Proportions of Sir Isaac Newton's 
Philosophy. Select Parts of Professor Saunders on' s 
Elements of Algebra for Students at the Universities 
was published in 1761. 

There seem to have been some grounds for 
Diderot's choice of Saunderson as a mouthpiece for 
his eighteenth-century illumination. Some criticism, 
in a very different tone from the Memoir prefixed 
to his life, appears as an article in the Biographia 
Britannica,^ signed P. "He was supposed not 
to entertain any great notion of revealed religion " 
(writes P.), *' yet we are told he appointed to receive 

' Memoirs of the Life and Character of Dr Nicholas Saunderson, in 
Saunderson's Algebra (ed. 174.)), vol. i, p. 12. 
'"* Vol. vi, part ii (1766), pp. : 58- 159. 



1 8 DIDEROT'S PHILOSOPHICAL WORKS 

the sacrament the evening before his death. " Further 
details of his character added by P. are not quite in 
keeping with Diderot's ideal Saunderson. "As to 
his character," we are told, "it is well observed that 
he was a man rather to be admired than loved. He 
had, indeed, much wit and vivacit}' in conversation, 
so that none could be a better companion ; but like 
his predecessor Mr VVhiston, he uttered his senti- 
ments of men not only freely but licentiously, with 
a kind of contempt and disregard for decency and 
commonsense ; and which is worse, he indulged 
himself in women, wine, and profane swearing to a 
shocking excess ; by which means he did more hurt 
to the reputation of the mathematics than he did 
good by his eminent skill in the science." The 
EncyclopcEdia ^ admits the account of his dying 
moments to be entirely false {ahsohiineftt supposee), 
and that it was considered as a crime against learn- 
ing {un crime de lese-eruditio7i). In the account in 
the Memoir'- we read that he was informed by 
Mr Gervase Holmes that there was no hope of his 
recovery. ' ' He received this notice of his approach- 
ing death with great calmness and serenity ; and 
after a short silence resumed life and spirits, and 
talked with as much composure of mind as he had 
done in his most sedate hours of perfect health. 
He appointed the evening of the following day to 
receive the sacrament with Mr Holmes ; but before 
that came he was seized with a delirium, which 
continued to his death." / 

> Art. Aveiigle. - P. xix. 



INTRODUCTION 19 

In the Letter of Mr Gervase Holmes .0 the 
Author of the Letter on the Blind, containing the 
true accouttt of the last hours of Saounderson (sic), 
a little volume printed at Cambridge, 1750, the 
author finds Diderot's Letter "ingenious," and he 
adds, "I wish I could say judicious.'' He then 
proceeds to give the history of the last moments of 
Saunderson, and after having denied the possibility 
of Saunderson in his last moments pronouncing the 
long discourse Diderot attributes to him, he puts 
another, and a much longer one, in his mouth, which 
is diametrically opposed to it. The book, dated 
14/25 December 1749, is quoted in a note on the 
edition of Diderot in twenty volumes by MM. Assezat 
and Tourneaux, but no copy of it is to be found in 
the British Museum, the Bodleian Library, or the 
University Library at Cambridge. 

The Date of the Letter 

Diderot attached himself to Madame de Puisieux 
in 1745, and his passion for her lasted until he dis- 
covered her infidelity in 1749.^ She was needy, and 
when Diderot received fifty louis for the Essay on 
Merit and Virtue'^ he gave them to her. Shortly 
afterwards she was again in need of money, and 
he gave her the fifty louis which he had received 

' Madame de Puisieux crime to visit him when a prisoner on parole 
at Vincennes. He became jealous, and, seeing her very much dressed up 
one day, asked her where slie was going. " To a fete at Champigny." 
" Alone?" " Yes." Diderot distrusted her, and escaped over the wall 
of the park to Champigny, wiiere he saw his mistress with a lover. He 
returned to Vincennes. 

^ Essai sur le myrtle et la verhi ( 1 745). 



20 DIDEROTS PHILOSOPHICAL WORKS 

for his PJiilosophic Thoughts,^ which was written, 
Madame de Vandeul says, between Good Friday 
and Easter Day. "The novels of Crebillon being 
then popular," she continues, " my father talked to 
Madame de Puisieux about the composition of this 
libertine literature. He declared that the main 
thing was to find some amusing idea as a hinge for 
the whole story, and that licentious wit took the 
place of taste. She defied him to write a book of 
this nature, and at the end of a fortnight he brought 
her The Indiscreet Jewels and fifty louis. The needs 
of Madame de Puisieux induced him to publish the 
Letter on the Deaf and Blind, ^ and he attended all 
the experiments which bore upon this subject. 

" Monsieur de Reaumur had in his house a man ^ 
blind from birth, and operated on him for cataract. 
The removal of the dressing for the first time was 
supposed to take place before some doctors and a 
few men of letters, and among them my father was 
present. He hoped for an interesting and no\el 
investigation, as he was anxious to investigate the 
effect of light for the first time upon a person to 
whom it was hitherto unknown. The dressing was 
removed, but the conversation of the blind man 
proved conclusively that he had already seen. The 
spectators were not satisfied ; some spoke indis- 
creetly as the result of the others^ ill-humour ; and one 
person said that the first experiment had taken place 

' Pens^es Phiiosophiques (1746). 

^ Lettre sur les Aveugles, a r usage de ceux qui voieni (ij^g). 

^ Actually a blind girl. 



INTRODUCTION 21 

in the presence of Madame Dupre de Saint Maur. 
My father left, saying that Monsieur de Reaumur 
preferred the eyes of a senseless pretty woman to 
the presence of intelligent witnesses. 

" This saying displeased Madame Dupre de Saint 
Maur, who considered it an insult to her eyes and 
her knowledge of anatomy, for she laid claim to 
scientific knowledge. She egged on Monsieur 
d'Argenson ^ (who found her charming), and not 
many days after, on July 24th, 1749, an officer named 
Rochebrune with three men visited my father at nine 
o'clock in the morning, and, after thoroughly examin- 
ing his study and his papers, drew from his pocket an 
order to arrest him and take him to Vincennes."^ 

He was imprisoned for twenty-eight days without 
seeing anyone but Monsieur Berryer, then lieutenant 
of police. Monsieur Berryer advised him to address 
himself to Monsieur d'Argenson, and undertook to 
deliver the letter. After twenty-eight days Madame 
Diderot was ordered to go to Vincennes ; and Diderot 
was taken to the Chateau and informed that the king 
by an excess of clemency ' ' allowed him to be a 
prisoner on parole and take exercise in the park." 
The Marquis du Chatelet,the Governor, was very kind 
to him, and did his best to lighten his stay. He and 
Madame Diderot remained there for three months, 
after which they were allowed to return home. 
During his close imprisonment he found means of 
writing in an ingenious manner. He had a tooth- 

* Then Minister of War. 

^ Mimoires pourservir a ^hisloire de la vie et des onvrages de Diderot. 



22 DIDEROT S PHILOSOPHICAL WORKS 

pick in his pocket, of which he made a pen ; he 
knocked off a slate near his window, ground it to 
powder, moistened it with wine, and made an ink- 
pot of a broken glass. Having in his possession a 
volume of Milton's Paradise Lost, he iilled the blank 
leaves and spaces with reflections on his position and 
notes on the poem. ^Always anxious to give his 
fellow-men the advantage of his discoveries, he 
wrote, says Naigeon, above the door of a room : 
" Ink is made with slate ground to a very fine 
powder and wine, and a pen of a tooth-pick." 

It is possible that Madame Dupre de Saint Maur's 
instrumentalit}- in Diderot's arrest has been too much 
emphasised, for the Government was then only too 
ready to proceed against one of the boldest of the 
French philosophes. Assezat ^ adduces as a reason 
for thinking that Diderot's arrest was not solely due 
to the influence of Madame Dupre de Saint Maur 
the following note by the Marquis d'Argenson in his 
Memoirs : — " August, 1749. There have been these 
last few days a number of abbes, savants, and in- 
tellectuals arrested, and taken to the Bastille, such 
as Diderot, some professors at the University, 
doctors of the Sorbonne, etc. They are accused of 
having written verses satirising the king, and of 
having recited and made them public, of having 
intrigued against the ministry, of having written 
and printed works advocating deism and immorality. 
This had to be suppressed as their licence had become 

^ Notice Preliminaire to the Lettre stir les Avettgles, a'uvres com- 
pletes de Diderot, ed. J. Assezat (1875), ^o^- 'j P- 278. 



INTR OD UCTION 2 3 

excessive. This is my brother's doing, who shows 
himself in this a great minister." 

In another note, dated August 21st in the same 
year, the Marquis adds: "One Diderot by name, 
author of TJie Indiscreet Jewels and The CUar-sigJited 
Blind Man (the Letter on the Blind), has been inter- 
rogated in his prison at Vincennes. He received 
the ijiagistrate (some say the minister) with the 
boldness of fanaticism. The Interrogator said : 
' You are insolent, and you will remain here a long 
time.' This Diderot, when he was arrested, had just 
written an amazing book against the religion, which 
is entitled The Tomb of Prejudices. " ^ 

Letter on the Deaf and Dumb 

The following note is prefixed to the Letter on 
the Deaf and Dumb in Assezat's edition of Diderot : ^ 
"Between the Letter on the Blind and the Letter 
on the Deaf and Dumb Diderot had begun to 
publish the Encyclopcedia, and it was during the first 
period of this long and feverish toil, which was to 
last thirty years, that he found time to answer the 
Abbe Batteux' work, The Fine Arts reduced to a 
Single Principle. The Letter is addressed to the 
author whom Diderot criticises ; it show no signs 
of the haste with which the notes — collected as 

^ Perhaps the Marquis d'Argenson means The Sceptic's Walk {La 
Promenade du Sceptiqiie), written in 1747. Madame de Vandeul has 
told us that an agent named d'Heniery seized it. The MS. passed 
from the library of Monsieur Berryer, lieutenant of police, into that of 
Monsieur de Lamoignon, and then into that of Monsieur Beaujon. It 
was first published in 1830. — (A) 

* Vol. i, p. 345. 



24 DIDEROT S PHILOSOPHICAL WORKS 

material for the Encyclopcedia — were put together. 
Indeed, Diderot shows a great deal of tact, polite- 
ness, and ingenuity in this work." 

The Letter on the Deaf and Dumb for the Use of 
those who Hear and Speak, written in 175 1, 
touches upon one or two points in the line of 
thought of the Letter on the Blind. 

There has been a considerable amount of dis- 
cussion about an idea which holds a prominent 
place in this Letter — that of a "theoretical mute" 
(muet de convejttion). Was the idea borrowed by 
Condillac from Diderot ? It must be remembered 
that Diderot was very intimate at this period with 
Condillac, who had introduced Rousseau to him ; 
and Rousseau tells us in his Confessions that the 
three men dined together every week at the " Panier 
fleuri, " The idea might have arisen naturally in 
their meetings, or the germ of it might have been 
developed independently by both Diderot and 
Condillac. 

Diderot expresses his idea as follows: "My 
idea would be to decompose a man, so to speak, 
and to examine what he derives from each of the 
senses with which he is endowed. ... It would 
be amusing to get together a society, each member 
of which should have no more than one sense ; 
there can be no doubt that they would all treat one 
another as out of their wits." This was said at the 
time to be the source of the statue in Condillac's 
Treatise on the Sensations (1754). Condillac's 
statue was organised like a man, but with each 



INTRODUCTION 25 

sense called into being singly, at the will of an 
eternal arbiter.^ Smell, and then other senses, 
are imparted to it in turn, each increasing the 
statue's stock of ideas. As the Treatise on the 
Sensations was published three years after Diderot's 
Letter on the Deaf a7id Dumb, Condillac was accused 
of borrowing the idea, and he wrote a pamphlet ^ 
defending himself from the charge, and asserting 
that the idea of the statue was suggested to him by 
a Mademoiselle de Ferrand. 

" Of the part of the Letter \.\\.?i\. concerns gesture," 
writes Lord Morley,^ "one can only say that 
it appears astonishingly crude to those who 
know the progress that has been made since 
Diderot's time in collecting and generalising the 
curious group of facts connected with gesture- 
language. We can imagine the eager interest that 
Diderot would have had in such curious observa- 
tions as that gesture-language has something like a 
definite syntax ; that it furnishes no means of dis- 
tinguishing causation from sequence or simultaneity ; 
that savages can understand and be understood with 
ease and certainty in a deaf-and-dumb school."^ 

As was his custom, Diderot contented himself 
with throwing out a suggestion, and then broke 
away into the entirely different field of aesthetics. 

' Morley, Diderot, vol. i, p. io6. 

'^ R^ponse a un reproche qui rtia ^W fait sur le projet exicut^ dans le 
Traits dds Sensations, Giuvres, tome iii, p. 321. Paris, Briere, 1821. 

•• Morley, Diderot, vol. i, p. 107. 

* Tylor's Researches into the Early History of ATankind, chapters ii 
and iii. Lubbock's Origin of Civilisation, chapter ix. 



The notes accompanying this translation are signed as follows ; 



(r) Notes from the original edition 

(2) ,, Naigeon's edition 

(3) ,, Belin's edition 

(4) ,, Briere's edition 

(5) ,, Assezat's edition 

(6) Translator's notes 



signed (D = Diderot). 

(N). 

(B). 

(Br). 

(A). 

[ ]■ 



PHILOSOPHIC THOUGHTS 

Quis leget hasc. — Pers. Sat. i. 2. 

I WRITE of God ; I count on a very few readers ; 
and do not hope to find many in agreement with 
me. If these thoughts please nobody, they are 
certainl)^ bad, but I should count them sorry stuff 
if they were to everybody's taste. 

I 
People are for ever declaiming against the 
passions ; they attribute to them all the pains that 
man endures, and forget that they are also the 
source of all his pleasures. It is an ingredient in 
man's constitution which cannot sufficiently be 
blessed and banned. It is considered as an affront 
to reason if one ventures to say a word in favour 

of its rivals ; yet it i^ pa^f^iorm 7\\c\x\p anH <trnng 7 

passions^ that can elevq tr tb^ ^"^"^ *''"' [C^^^ t-lii'ngg i 
Without them, there is no sublime, either in 
morality or in achievement ; the fine arts return to 
puerility, and virtue becomes a pettifogging thing. 

II 
Sober passions make men commonplace. If I 
hang back before the enem>', when my country's 

27 



28 DIDEROT S PHILOSOPHICAL WORKS 

safety is at stake, I am but a poor citizen. My 
friendship is but self-regarding if my friend's peril 
leaves me considering my own danger. If life is 
dearer to me than my mistress, I am a poor lover. 

Ill 

Deadened passions degrade men of extraordinary 
quality. Constraint annihilates the grandeur and 
energy of nature. Look at that tree ; it is to the 
luxury of its branches that you owe the coolness 
and breadth of its shade, which you may enjoy 
until winter despoils it of its leafy honours. There 
is no more excellence in poetry, in painting, and 
in music when superstition has wrought upon the 
human temperament the effect of old age. 

IV 

fW^ Tt_jiVoilld_ be fortunatp, ppoplg__jvij_l_ say to me, 

, _ fpr a m^-o—t Q \\-xve. strong- j ^assions ? Certainly, if 

y^ tj^ey,,ag e - all in ha rmony. EstaBHsEajust harmony 

among them, and you need fear no convulsions and 

\ disorders. If hope be balanced by fear, the point 

^ ■ of honour by love of life, the taste for pleasure by 

y ,VV consideration for health, there will be no libertines, 

yV^ nor rufflers, nor poltroons. 

V 

It is the very height of madness to propose the 
ruin of the passions. A fine design, truly, in your 
devotee, to torment himself like a convict in order 
to desire nothing, love nothing, and feel nothing. 



j3H>-3tf>^ 



PHILOSOPHIC THOUGHTS 29 

He would end by becoming a monster, if he were 
to succeed. -.. y^AjM^ 

Can what is the object of my respect in one man 
be the object of my scorn in another ? Certainly 
not. Truth, independent!}- of my caprices, should 
be th e rule of my judgments, and I shall not call 
that_ quality a crime in one man which 1 admire 
a s a virt ue jn another. Am I to think that the 
practice of self-improvement is to be restricted to 
some few, when nature and religion inculcate it 
on all alike? Whence comes this monopoly? If 
Pachomius did well in separating himself from the 
human race and burying himself in a wilderness, 
I may follow his example, and in imitating him I 
shall be equally virtuous ; and I see no reason why 
a hundred others may not have the same right. 
Yet it would be a strange sight to see an entire 
province, dismayed at the dangers of society, dis- 
persed in forests, the inhabitants living like wild 
beasts to sanctify themselves, and a thousand pillars 
rising above the ruins of all social ajffections ; 
a new race of Stylites stripping themselves from 
religious motives of all natural feelings, ceasing 
to be men and becoming statues in order to be 
true Christians. 

VII 

What voices, what cries, what groans ! Who 
has shut up in dungeons all these piteous wretches ? 
^^ '""at crimes have all these creatures committed ? 




^^ ^ 30 DIDEROT S PHILOSOPHICAL WORKS 

Some beat their breasts with stones, others lacerate 
their body with iron nails, all express in their eyes 
regret, pain, and death. Who condemns them to 
such torments ? TJie God whom they have offended. 
Who then is this God ? A God full of goodness. 
But would a God full of goodness take pleasure in 
bathing himself in tears ? Are not these fears an 
insult to his kindness? If criminals had to appease 
the fury of a tyrant, what more could they do ? 



^/ 



VIII 



\^ These are people of whom we ought not to say 

that they fear God, but that they are mortally afraid 
of him. 



y 






IX 

Judging from the picture they paint of the 
Supreme Being, from his tendency to wrath, from 
the rigour of his vengeance, from certain comparisons 
of the ratio between those he abandons to perish 
and those to whom he deigns to stretch out a hand, 
the most upright soul would be tempted to wish 
that such a being did not exist. We would be 
happy enough in this world, if we were assured we 
had nothing to fear in another. The thought that 
a God did not exist has never terrified humanity, 
but the idea that a God such as is represented exists. 

X 

God must be imagined as neither too kind nor too 
cruel. Justice is the mean between clemency and 



PHILOSOPHIC THOUGHTS ^i ^^ 

cruelty, just as finite penalties are the mean between 
impunity and eternal punishment. 

XI 

I am aware that the sombre ideas of superstition 
are more generally approved of than accepted ; that 
there are pietists who do not think it necessary to 
hate themselves in order to love God, or to live as 
desperate wretches, in order to be religious ; their 
devotion is a smiling one, their wisdom very human ; 
but whence comes this difference in sentiment be- 
tween people who prostrate themselves before the 
same altars ? Can piety thus be subject to the law 
of temperament ? Alas! it must be so. Its influence 
is only too apparent in the same devotee : he sees, 
in accordance with its variations, a jealous or a 
merciful God, and hell or heaven opening before 
him ; he trembles with fear or burns with love ; it 
is a fever with its hot and cold fits. 

XII 

Yes, I maintain that sup erstition is more o f an tT^ 
i nsult to God than atJ ieism. " I would rather," 
said Plutarch, " that people thought that a Plutarch 
never existed, than that they thought of Plutarch 
as unjust, choleric, inconstant, jealous and revenge- 
ful, and such as he would be sorry to be." 

XIII 

Only the deist can oppose the atheist. The 
superstitious man is not so strong an opponent. 



32 DIDEROT'S PHILOSOPHICAL WORKS 

His God is only a creature of the imagination. 
Besides difficulties of a material nature, he is 
exposed to those which result from the falsity 
of his notions. A C — and a S — would have been u 
a thousand times more embarrassing to a Vanini 
than all the Nicoles and Pascals in the world. -^ 



XIV 

Pascal was an upright man, but he was timid and 
inclined to credulity. An elegant writer and a pro- 
found reasoner, he would doubtless have enlightened 
the world, if Providence had not abandoned him to 
people who sacrificed his talents to their own anti- 
pathies. How much it is to be regretted that he 
did not leave to the theologians of his day the task 
of settling their own disputes ; that he did not give 
himself up to the search for truth without reserve 
and without fear of offending God, by using all the 
intellect God had given him ! How regrettable that 
he took for his masters men who were not worthy 
to be his disciples ! One could say of him, as La 
Mothe said of La Fontaine, that he was foolish 
enough to think Arnauld, de Sacy, and Nicole 
better men than himself. 

XV 

" I tell you that there is no God ; that Creation 
is a fiction ; that the eternity of the universe is no 

[^ Vanini, 1 585-1619, was executed at Toulouse in 1619, on the 
charge of atheism. The initials C and S stand for the two English 
deists, Cud worth and Shaftesbury.] 



PHILOSOPHIC THOUGHTS 33 

more of a difficulty than the eternity of spirit ; that 
because I do not see how motion could have caused 
this universe (though it keeps it going), it is 
ridiculous to solve the difficulty by supposing the 
existence of a being of whom I can have no real 
conception ; that if the wonders of the physical 
universe show some intelligence, the confusions in 
the moral order are the negations of a Providence. 
I tell y j^u if ev erything is the work of a God, ev ery- 
t hing should be the best possible : for if everyth ing" is 
n ot the bes^ pn<;c;ih1p, it i^ ip ipn tence or ma levolence 
OJ1 the p ar t ng-G nd Therefore it is fortunate that I 
am not better informed as to his existence. If it 
were proved satisfactorily (and it is by no means 
proved) that all evil is the source of good, that it 
was for the best that Britannicus, the best of 
princes, perished, and that Nero, the worst of men, 
should reign, how is it possible to prove that it was 
impossible to attain the same ends without using 
such means ? To allow vice in order to throw 
virtue into relief is a poor advantage in comparison 
with its real disadvantage." 

That, says the atheist, is my case ; what have 
you to say to it ? " That I am a miserable wretch, 
and that if I had not J ling to fear from God, I should 
not be disputing his existence. " Let us leave such an 
answer to orators ; it may be untrue ; politeness 
forbids it and it has no savour of charity about it. 
Because a man is mistaken in his denial of God, 
should we insult him ? People only take refuge in 1 
invective when they run "sfiort of proofs. Of two ! 



34 DIDEROT'S PHILOSOPHICAL WORKS 

\ engaged in argument, it is a hundred to one that 
(the man in the wrong will become angry. "You 
/ thunder instead of answering," says Menippus to 
Jupiter; "are you then in the wrong?" 



XVI 

One day somebody asked a man if real atheists 
existed. Do you think, he responded, that real 
Christians exist ? 

XVII 

None of the vain speculations of metaphysics 
have the cogency of an argument ad Jioinmeni. In 
order to convince, it is sometimes only necessary 
to rouse the physical or moral instinct. The 
P^rhonist was convinced by a stick that he was 
wrong in doubting his own existence. Cartouche, 
pistol in hand, might have taught Hobbes a similar 
lesson : "Your money or your life ; we are alone, 
I am the stronger, and between us there is no 
question of justice." 

XVIII 
It is not from the metaphj^^ician that atheism 



has received its most vital attaclc The sublime 
meditations of Malebranche and Descartes were 
less calculated to shake materialism than a single 
observation of Malpighi's. If this dangerous 
hypothesis is tottering at the present day, it is to 
experimental physics that the result is due. It is 
only in the works of Newton, of Muschenbroek, of 



PHILOSOPHIC THOUGHTS 35 

Hartzoeker, and of Nieuwentit, that satisfactory 
proofs have been found of the existence of a reign 
of sovereign intelligence. Thanks to the works of 
these great men, t he wor ld is n o longer a God ; it 
i s a machine with its whe el s, its cords, its pulleys, 
its springs, and its weights. 

XIX 

The subtilties of ontology have at best made 
sceptics, and it was reserved for the knowledge 
of nature to make true deists. The discovery_of 
g erms alone ha s destroye d one of th^ _iiio st power - ■ 
ml arguments Qf__atiieijm. Whether motion be 
essential or accidental to matter, I am now con- 
vinced that its effects are limited to developments ; 
all experiments agree in proving to me that 
putrefaction alone never produced any organism, 
I can allow that the mechanism of the vilest insect 
is not less marvellous than that of man ; and I am 
not afraid of the inference that as an intestinal 
agitation of molecules is able to produce the one, it 
is probable that it has produced the other. If an 
atheist had maintained, two hundred years ago, 
that some day perhaps people would see men spring 
full-formed from the bowels of the earth just as we 
see a mass of insects swarm in putrefying fle sh, I U 
would like to know what a metaphysician would 
hi ci ve had to say to him ? ^ 



' Diderot here alludes to Redi's experiments about the generation of 
insects, and in the preceding Thought he alludes to the discoveries due 
*o the telescope and microscope. — (A) 






6 DIDEROT'S PHILOSOPHICAL WORKS 



XX 

It was in vain that I made use of scholastic 
subtilties against the atheist ; he found among his 
feeble reasons one argument of some validity, ' ' A 
multitude of useless verities are proved to me 
without any doubt," he said, "and the existence 
of God, the reality of moral good and moral evil, 
and the immortality of the soul are still problems 
for me. What ! Is it less important for me to be 
informed on these subjects than to be sure that the 
three angles of a triangle are together equal to two 
right angles ? " While like a skilful orator he made 
me taste the full bitterness of this reflection, I joined 
battle with him again with a question which must 
have appeared singular to a man flushed with his 
first success. "Are you a thinking being?" I 
asked. "Can you doubt it?" he answered with 
a pleased air. "Why not? What have I seen 
to prove it ? Sounds and movement^ ? But the 
philosoph er sees the same h i an anima l_to whpm_ he 
de nies the faculty of thought ; why should I^ allow 
you what Descartes reluses the ant ? Exter^ially, 
your actions are designed to give me that ir(ipres- 
sion ; I should be tempted to maintain that you do 
think, but reason suspends my judgment. Betvveen 
external actions and thought my reason tells me 
there is no essential connection ; it is possible that 
your antagonist thinks no more than his watch ; 
must one take for a thinking being the first animal 
taught to speak? Wlio has informed you that nil 



PHILOSOPHIC THOUGHTS 37 

m gja are not so many well-trained parrots ? " 
"That is very ingenious," he returned, "but it is 
not by motion or sounds but by the continuity of 
ideas, the connection between propositions, and the 
links of the argument that one must judge if a 
creature thinks. If there was a parrot which could 
answer every question, I should say at once that it 
was a thinking being. But what has this to do with 
the existence of a God? If you were to prove to 
me that the most intelligent man were perhaps but 
an automaton, should I be the more disposed to 
recognise an intelligent Being in nature?" " That 
is my affair," said I ; "but admit that it would be 
madness not to credit your brother men with the 
faculty of thought ? " "Of course, but what 
follows?" "It follows that if the universe — but 
why drag in the universe ? — if a butterfly's wing 
shows me proofs of an intelligence a thousand times 
stronger than the proof you have that your fellow- 
man thinks, it would be a thousand times more 
foolish to deny that God exists than to deny that 
your fellow-man thinks. I appeal to your know- 
ledge, to your conscience ! Ha ve you ever obs erved 
in a£y_inaii_-4iiore__mteIiigmi£e^ wisdom, 

anrWpaQrm phlpnpt;^ than in the_ _mp.chanism of an 
i nsec t ? Is not the Deity as clearly apparent in the 
eye of a flesh-worm as in the works of the great 
Newton ? What, does the formation of the world 
afford less proof of intelligence than its explana- 
tion? What a position !" " But," you reply, " I 
admit the faculty of thought in another the more 



38 DIDEROT'S PHILOSOPHICAL WORKS 

readily as I myself think." That is an analogy I 
admit I cannot use, but against this must be set 
the superiority of my proofs to yours. Is not the 
intelligence of a first cause more conclusively proved 
in nature by his works than the faculty of reasoning 
in a philosopher by his writings ? Remember, I 
only adduced a butterfly's wing, a flesh-worm's eye, 
when I could crush you with the weight of the 
entire universe. I am greatly deceived if this proof 
is not well worth the best that has ever issued 
from the schools. It is by this argument , and 
others equally simple, that^I afrfconvinced of the 
existence of a God, and not by dTose~Trssues 
of dry and metaphysical ideas which are better 
calculated to give to truth an air of falsity than 
to unveil it. 

XXI 

I open the pages of a celebrated professor ^ and 
I read: "Atheists, I concede to you that move- 
ment is essential to matter ; what conclusion do 
you draw from that ? That the world is the result 
of a fortuitous concourse of atoms ? You might 
as well tell me that Homer's Iliad or Voltaire's 
Henriade is the result of a fortuitous concourse of 
written characters." I should be very sorry to use 
that argument to an atheist ; he would make quick 
work of the comparison. According to laws of the 
anal}-sis of chances (he would say) I ought not 

^ Bricre in his edition says that Rivard, who was then professor of 
philosophy, is here meant, but the argument which follows is a well- 
known one. — (A) 



PHILOSOPHIC THOUGHTS 39 

to be surprised that a thing happens, when it is 
possible and the difficulty of the result is compen- 
sated by the number of throws. There is a certain 
number of throws in which I would back myself to 
bring 100,000 sixes at once with 100,000 dice. 
Whatever the definite number of letters with which 
I am invited fortuitously to create the Iliad^ there 
is a certain definite number of throws which would 
make the venture advantageous to me ; indeed, my 
advantage would be infinite if the number of throws 
permitted me were infinite. You grant me that 
matter exists from all eternity and that movement 
is essential to it. In return for this concession, I 
will suppose, as you do, that the world has no limits, 
that the multitude of atoms is infinite, and that 
this order which causes you astonishment nowhere 
contradicts itself. Well, from these mutual admis- 
sions there follows nothing else unless it be that the 
possibility of fortuitously creating the universe is 
very small but that the quantity of throws is 
infinite ; that is to say, that the difficulty of the 
result is more than sufficiently compensated by the 
multitude of throws. Therefore, if anything ought 
to be repugnant to reason, it is the supposition that 
— matter being in motion from all eternity, and 
there being perhaps in the infinite number of pos- 
sible combinations an infinite number of admirable 
arrangements, — none of these admirable arrange- 
ments would have ensued, out of the infinite 
multitude of those which matter took on succes- 
sively. Therefore the mind ought to be more 



JnN 



40 DIDEROT'S PHILOSOPHICAL WORKS 

astonished at the hypothetical duration of chaos 
than at the actual birth of the universe. 

XXII 

I ^div ide atheists in to t hree class es. There are 
some who tell you openTythere is no God, and are 
convinced of this ; these are genui ne athe ists : there 
is a fairly large number of people who do not know 
what to think and would be glad to decide the 
question by tossing up ; these are sceptical atheists : 
and a still larger number who wisnthere~were no 
God, and who pretend to be convinced of his non- 
existence and live in harmony with this conviction ; 
these are the . bragg adocios of the party. I detest 
braggarts ; they are dishonest : I pity genuine 
atheists ; all consolation is dead to them : and I 
pray God for the sceptics ; they lack knowledge. 



XXIII 

The deist maintains the existence of God, the', 
immortality of the soul and its consequences ; the '., 
sceptic has not decided on these points ; the atheist f 
denies them. The sceptic, therefore, has one more j 
motive for practising virtue than the atheist, and 
less than the deist. If it were not for fear of the 
laws, the natural tendency of a man's character, and 
the knowledge of the actual benefits of virtue, the 
probity of the atheist would be lacking in founda- 
tion, and that of the sceptic would be built upon a 
' ' perhaps. " 







^ 



PHILOSOPHIC THOUGHTS 41 

XXIV 

Scepticism does not suit everybody. It supposes 
a profound and careful examination. He who 
doubts because he is not acquainted with the 
grounds of credibility is no better than an ignor- 
amus. The true sceptic has counted and w^eighed 
his reasons. But it is no easy matter to weigh 
arguments. Which of us knows their value with 
any exactness ? Out of a hundred proofs of the 
same truth, each one will have its partisans. Every 
mind lias44s-ajiai_telescope. An objection which is 
invisible to you is a colossus to my eyes, and you 
find an argument trivial that to me is crushing in its 
efficacy. If we dispute about their intrinsic value, 
how shall we agree upon their relative ? Tell me 
how many moral proofs are needed to balance a 
metaphysical conclusion ? Are my spectacles in 
fault, or yours ? If, then, it is so difficult to weigh 
reasons, and if there are no questions which have 
not two sides, and nearly always in equal measure, 
how come we to cut knots with such rapidity ? 
How do we come by this convinced and dogmatic 
air ? Have we not a hundred times experienced 
how revolting is dogmatic presumption? "1 have 
been brought to detest probabilities," says the 
author of the Essays,^ "when they are foisted on 
me as infallible ; I love words which soften and 
moderate the temerity of our propositions, per- 
adventurc, in no wise, sojne people say, viei/iitiks, 
' Montaigne, book iii, ch. xi. 



42 DIDEROT'S PHILOSOPHICAL WORKS 

and the like ; and if I had to teach children I should 
so train them to answer in this hesitating and un- 
decided manner : ' IVJiat does that ineafi ? I do not 
understatid ; maybe; is it true?' that they would 
have the appearance of apprentices at sixty years of 
age, rather than of doctors at ten, as at present." 

XXV 

What is God ? A question we ask children, and 
that philosophers have much trouble in answering. 

We know the age when a child ought to learn to 
read, to sing, to dance, to begin Latin or geometry. 
It is only in religion that we take no account of his 
capacity. He hardly hears what you say before 
he is asked, "What is God?" It is at the same 
moment, and from the same lips, that he learns of 
the existence of ghosts, goblins, were-wolves — and 
a God ! He is taught one of the most important 
truths in a manner adapted to bring it into disrepute 
/one day before the bar of reason. W^ould it be at 
all surprising if, at twenty years of age, finding the 
existence of God confounded in his mind with a 
host of idle prejudices, he were to treat it as our 
judges treat an honest fellow who has fallen into 
bad company by some accident ? 

XXVI 



and another mistake is that Iiis presence is not 
sufficiently insisted upon. Men have banished God 



\ 



PHILOSOPHIC THOUGHTS 0^ ,7043 ^ 

from their company and have hidden him in a 
sanctuary ; the walls of a temple shut him in, he 
has no existence beyond. Fools that you are, 
break down these limitations that hamper your 
ideas ; set God free ; see him everywhere, as he is 
everywhere, or say that he is non-existent. If I 
had a child to bring up, I would make his God his 
companion in such a real sense that he would 
perhaps find it less difficult to become an atheist, 
than to escape his presence. Instead of confront- 
ing him with a fellow-man (whom maybe he knows 
to be worse than himself) I would say outright : 
" God hears you and you are lying." Young people 
are influenced by their senses. I would multiply 
about him symbols indicating the divine presence. 
If there were a gathering at my house, I would 
leave a place for God, and I would accustom him to 
say : ' ' We were four — God, my friend, my tutor, 
and myself," 

XXVII 
Ignorance and incuriosity are two soft pillows, 
but to find them so we must have a head as well 
contrived as Montaigne's.^ 

XXVIII 

Vigorous minds and ardent imaginati ons do no t 
take knidly ro the mdolencc of scepticism. The}^ 

wouIH rather risl^ -a cfroicc than make no ne ; be 

deceived than live in doubt. Whether they do not 

^ "Oh, que c'est un doulx et mol chevet, et sain, que I'ignorance ct 
I'incuriosite, a reposer une teste l>ien faicte," Essais, liv. iii, ch. xiii. 



44 DIDEROT'S PHILOSOPHICAL WORKS 

trust their arms, or whether they fear deep waters, 
we see them always clinging to branches they know 
to be fragile. They would rather be caught on 
these branches than abandon themselves to the 
torrent. They are sure of everything, though they 
have investigated nothing carefully ; they question 
nothing because they have neither the patience nor 
the courage. They make their way by broken 
lights, and if by chance they come across the truth, 
it is not by searching, but suddenly and, as it were, 
by revelation. They are among the dogmatic group 
what the illuminati are among the pietists. I have 
seen individuals of this restless tvpe^ __who could n^ t 
conceive how tranquillity of mind could be allied 
with scepticism. "How can one live happilv 
without knowing what o ne is, whence one come s, 
whither o ne goes, wh y we are here ? "_ "I make 
a point of my ignorance on all these questions, and 
am not distressed," replies the sceptic coolly; "it 
is not my fault if my reason is mute when questioned 
on my state. All my life I shall live in ignorance j 
of what it is impossible for me to know, and be none ' 
the worse for it. Why should I regret knowledge 
which I could not attain, and which is doubtless 
unnecessary to me, since I have it not ? I would 
as soon make myself wretched, says one of the 
greatest geniuses ^ of our age, because I am not 
equipped with four eyes, four feet, and two wings. " 
^ Voltaire. 



PHILOSOPHIC THOUGHTS- ^^-^' 

XXIX- ACP-/' ~ A^ "^''-'- 

A search for truth should be required of one, but 
not its attainment. May not a sophism affect me 
as deeply as a solid proof? I am obliged to admit 
the falsehood that I take to be the truth, and to 
reject the truth that I take for a falsehood ; but how- 
am I to blame, if I am deceived from no fault of mine? 
We are not rewarded in the next world for using 
our intelligence in this ; ought we to be punished 
for a lack of it ? To damn a man for foolish reason- 
ing is to forget that he is a fool, and to treat him 
as a criminal. 

XXX 

What is a sceptic ? A philosopher who has 



questioned all he believes, and who believes what 
a^ legitimate use of hi s reason and his senses has 
proved to him to be true. Do you w ant a more 
precise definition ? Makg a|Pyrrhonistyincere, and 
you have the sceptic. 



XXXI 

What has never been put in c[uestion has not been 
demonstrated. What people have not examined 
without prepossession has never been examined 
thoroughly. Sce pticism is thus the first step to- \ 
w ards truth . It must be applied generally, for it 
is the touchstone. If to ascertain the existence of 
God the philosopher begins by questioning it, is 
there any proposition which should not be so tested ? 



46 DIDEROPS PHILOSOPHICAL WORKS 

XXXII 

Incrsdulit:v;Ljs . sometimes the vice of a Foolr and 
credulity^he def ect^^of^_a^jTian__of intelligence. The 
latter sees far into the immense ocean of possibilities, 
the former scarcely sees anything possible but the 
actual. Perhaps this is what produces the timidity 
of the one, the temerity of the other. 

XXXIII 

It is as hazar dous to believe too much a^ oolittle. 
The danger of bemg-'a^olytheist is neither greater 
nor less than the danger of being an atheist ; now 
scepticism is the only defence, in any period and in 
any place, against these two opposite extremes. 



XXXIV 

A half-hearted scepticism is the mar k of a feeble 
understanding which reveats a pusnT a^nirnous reasoner 
whoIp£XP\[ts~h 1 m setf^1^ J3-e''grta rm e^by consequences, 
a superstitious creature who thinks to honour God 
by ^imposin CT__ fpttpr^~2 nfr-hftr reag;nn 3 "c;pen>s of un- 
believer who is afraid of unmasking himself to him- 
self. For if truth has nothing to lose b}- examination, 
as is the demi-sceptic's conviction, what does he 
think in the bottom of his heart of those privileged 
notions which he fears to investigate, and which are 
hidden in a recess of his brain, as in a sanctuary 
which he dares not approach ? 



PHILOSOPHIC THOUGi..,.,,^ 

IS 49 

XXXV ^ before 

I hear cries against impiety on every side. i . 
Christian is impious in Asia, the Mussulman in 
Europe, the papist in London, the Calvinist in 
Paris, the Jansenist at the top of the rue St 
Jacques, the Molinist at the bottom of the faubourg 
St Medard. What is an impious person, then ? 
Either everybody, or nobody. 

XXXVI 
When the pious declaim against scepticism, it 
seems to me that they either do not understand 
their own interest, or are inconsistent. If it is 
certain that a true faith, to be embraced, and a 
false faith, to be abandoned, need only be fully 1 
known, surely it must be highly desirable that 
universal doubt should spread over the surface of 
the earth, and that every race should consent to 
the examination of the truth of its religion. Our 
missionaries would find a good half of their work 
already accomplished. 

XXXVII 

He who does not delib er ately embrace the faith 
i n which he has been bred can no more p lume him- 
self on b eing a Christian or a Mussulman than upo n 
not being b orn blind or lame. It is his luck, not 
his merit. 

XXXVIII 

He who would die for a faith whose falsity he 
was aware of, would be a madman. He who dies 



46 DIDERrOTS PHILOSOPHICAL WORKS 

-se faith, which he thinks a true one, or for 
-lUe faith of whose truth he has not been con- 
vinced by proofs, is a fanatic. 

The true mart yr is he who dies for a tniR_f arth, 
whose truth has been clearly proved to him. 

XXXI X 

T he tr ug marfyr wgjt'i for Hp;^th, the enthusi ast 
rushes towards it. 



XL 

He who at Mecca would insult the ashes of 
Mahomet, overturn his altars and disturb a mosque, 
would be certainly impaled and perhaps would not 
be canonised. Such zeal is not now in fashion. 
Folyeucte in our days would be a madman. 

XLI 

The age of revelations, of prodigies, and of extra- 
ordinary missions is no more. Christianit}' has 
no longer need of this scaffolding. A man who 
took it into his head to play the part of Jonah 
amongst us, and rushed about the streets crying, 
"In three days Paris will be no more. Parisians, 
repent, cover yourselves with sackcloth and ashes, 
or in three days you will perish," would be seized at 
once, and taken before a judge, who would certainly 
send him to the lunatic asylum. It would be no 
use his saying to us, "Does God love you less than 
the men of Nineveh : are you less guilty ? " No one 
would waste his time in answering him, nor would 




PHILOSOPHIC THOUGHTS 49 

wait until the date of his prophecy expired before 
treating him as a visionary. 

EHjah may return from the other world when he 
pleases ; men are such that it would be a miracle 
indeed if he were well received in this. 

XLII 

When a dogma which contradicts the dominant 
religion, or some event which is inconsistent with 
the tranquillity of the public, is announced, even if 
the mission is justified by miracles, the government 
does well in dealing rigorously, and the people in 
crying "Crucify." How dangerous to abandon the 
people to the seductions of an impostor, or the 
dreams of a visionary ! If the blood of Jesus Christ 
cried for vengeance against the Jews, 'tis because in 
shedding it they turned a deaf ear to Moses and the 
Prophets who foretold the Messiah. If an angel 
came down from heaven and supported his argu- 
ments by miracles, and yet preached against the 
law of Christ, Paul would call him anathema. I t_is 
not, theref ore, by miracles that a man's mission is 
to be judged, but by the conformity of his doctrine 
with that of the people to whom he declares himself 
sent, especi ally wJien the doctrine of that people is 
proved to be true. 

" XLIII 

Every innovationJn a gover nment is to be feargt lT \ 
The holiest and best of religions, even Christianity, 
did not make its way without causing some dis- 

4 



50 DIDEROT'S PHILOSOPHICAL WORKS 

turbances. The first sons of the Church more than 
once exceeded the limits of the patience and modera- 
tion recommended to them. Let me here quote some 
fragments of an edict of the Emperor JuHan which 
are very characteristic of the genius of that philosophic 
prince and of the humours of the zealots of that day. 
" I had imagined," says Julian, "that the leaders 
of the Galileans would be sensible of the difference 
between my methods and those of my predecessor, 
and that they would be grateful. Under his reign 
they suffered exile and imprisonment and a number 
of those they called heretics were put to the sword. 
Under my reign the exiles were recalled, the 
prisoners released, and the proscribed given again the 
possession of their goods. But such is the restless- 
ness and fury of this sect that since they have lost 
the privilege of mutual destruction, of tormenting 
those who are attached to their belief and those 
who belong to the religion authorised by the laws, 
they spare no effort and let pass no occasion to 
stir up revolt. They are people without regard for 
true piety and without respect for our ordin- 
ances. . . . Yet we do not drag them to our altars, 
nor do them violence. ... As to the poorer 
classes, it seems that they are stirred to sedition by 
their leaders, who are enraged at the limits we 
have set to their powers ; for we have excluded 
them from our courts of law, and they have no 
longer the power to make away with wills and 
supplant the legitimate heirs, and take possession 
of inheritances. . . , That is why we forbid the 



. ' ' I- 

PHILOSOPHIC THOUGHTS 51 

people to assemble factiously and to intrigue at the 
homes of its seditious priests. . , . Let this edict 
strengthen the hands of our magistrates who have 
been more than once insulted by these insurgents, 
and ran the risk of being stoned. Let them meet 
peaceably at their leaders, and pray there, let them 
there receive instruction and conform to their 
religion ; we permit this so long as they refrain 
from all sedition. If their meetings are an oppor- 
tunity for revolt and faction, they and their property 
will suffer, I warn them. Unbelievers, live in 
peace . . . and you who have remained faithful 
to the religion of your country and the gods of your 
fathers, do not persecute your fellow-men, your fellow- 
citizens, who are rather to be pitied for their ignorance 
than blamed for their wickedness, i^isby reason 
and not by vio lence that men should be brought to 
the tr utlT! We enjoin therefore upon you all, our 
faithful subjects, to leave the Galileans in peace." 

Such were the sentiments of this prince who can 
be accused of paganism, but not of apostasy. He 
passed the early years of his life under different 
masters and in different schools, and made an 
unhappy choice in later life. He unfortunately 
decided in favour of the faith of his ancestors and 
the gods of his country. 

XLIV 

I am astonished that the works of this learned 
Emperor have been preserved to us. They contain 
passages which, though they do not affect the truth 



52 DIDEROT'S PHILOSOPHICAL WORKS 

of Christianity, are by no means complimentary to 
certain Christians of his time, and the Fathers of 
the Church paid the works of their enemies the 
singular attention of suppressing them. It is 
apparently from his predecessors that Gregory the 
Great derived the barbarous zeal against art and 
letters which inflamed him. If this Pontiff had 
had his way we should be in the plight of the 
Mahometans, who have only the Koran to read. 
What would have been the fate of the writers of 
antiquity at the hands of a man who committed 
solecisms from religious motives, who thought that 
to observe grammatical rules was to set Jesus Christ 
below Donatus, ^ and who thought himself obliged 
to complete the ruins of antiquity ? 

XLV 

The divinity of the Holy Scriptures is not, how- 
ever, so clearly apparent therein, that the authority 
of the sacred historians is completely independent of 
the testimony of profane authors. Where should 
we be, if we had to find the finger of God in the 
literary form of our Bible? What sorry stuff is 
the Latin translation ! And even the originals 
are not exactly masterpieces of composition. The 
prophets, apostles and evangelists wrote as they 
pleased. If we were permitted to regard the 
history of the Jews purely as a production of the 
human mind, Moses and his continuators are no 
rivals of Livy, Sallust, Caesar, and Josephus, who 
^ A Latin grammarian. 



PHILOSOPHIC THOUGHTS 53 

are not suspected of being inspired. Is not the 
Jesuit Berruyer preferred to Moses? In our 
churches there are preserved pictures which we are 
assured are the work of angels and of the Deity 
himself. If these pictures were actually the work 
of Le Sueur or Le Brun, what could I find to say 
against this immemorial tradition ? Perhaps nothing 
at all. But when I look at these celestial works, 
and see the rules of painting violated at every 
moment both in design and execution, and the truth 
of art everywhere absent, since I cannot suppose 
the author an ignoramus, I must accuse the tradi- 
tion of falsity. I might make use of this analogy 
between these pictures and Holy Writ, if I were not 
well aware that it is immaterial whether their con- 
tents are well or ill written. The prophets' forte 
was telling the truth, not elegant composition. 
The Apostles died for the truth of what they 
preached and wrote, and for nothing else. But, to 
return to the matter under discussion, those profane 
writers should have been preserved who must have 
harmonised with sacred historians, — at any rate upon 
facts such as the existence and miracles of Christ, 
the qualities and character of Pontius Pilate, and the 
deeds and martyrdom of the early Christians. 

XLVI 

An entire nation, you will say, witnesses to this 

fact ; dare you deny it ? Yes, I dare, since it is 

not confirmed by the authority of someone not of 

your side, and I do not know whether that person 



L 



'^^ 



54 DIDEROT S PHILOSOPHICAL WORKS 



V. is free from fanaticism and delusion. Moreover, 

«j if an author of declared impartiality tells me that 

' a chasm opened in the midst of a city, that the 

vip gods when consulted about this event answered that 

>J it would close if the most precious possession was 

^^T ' thrown into it, and that a brave knight leapt in 

and that the oracle was fulfilled ; — I should be far 

^ less inclined to believe him than if he had simply 

f said that a chasm opened, and that considerable 

j^~\( time and labour were required to fill it. The less 

'' j probability a f act has the more does the testimony 

.' of--^!H lsIory~lose ljl^._ _weigh j>. I should make nxr- 

difficulty in believing a single honest man who 

should tell me that His Majesty had just won a 

complete victory over the allies ; but if all Paris 

were to assure me that a dead man had come to 

life again at Passy, I should not believe a word of 

it. That a historian should impose upon us, or that 

a whole nation should be deluded — there is no 

miracle in that ! 

XLVII 

Tarquin proposed to increase the corps of 
cavalry that Romulus had formed. An augur 
declared all change in the army sacrilegious, 
unless authorised by the gods. Angered at the 
opposition of the priest and determined to make an 
end of him and of an art which opposed his will, 
Tarquin had him summoned to the market-place, 
and said to him, "Soothsayer, is what I am think- 
ing of possible? If your knowledge is what you 



PHILOSOPHIC THOUGHTS 55 

boast it to be, you will be able to answer me." 
The augur was not embarrassed, but consulted the 
birds and made answer : ' ' Yes, Prince, what you 
propose is possible." Then Tarquin, drawing a 
razor from beneath his gown and taking a pebble, 
said to the augur, "Come here and cut me this 
pebble with this razor, for I thought this possible." 
Navius, for this was the augur's name, turned to the 
people and said composedly, " Strike the pebble with 
the razor, and may 1 be dragged to torture on the 
spot if it is not immediately divided." People saw, 
with surprise, the hardness of the pebble yield to the 
blade ; it was divided so promptly that the razor 
reached Tarquin's hand and drew blood. The 
astonished people applauded, and Tarquin re- 
nounced his scheme, and declared himself the 
protector of augurs. The razor and the fragments 
of the pebble were buried beneath an altar. A 
statue was put up to the augur, which was still in 
existence in the reign of Augustus, and both sacred 
and profane writers bear witness to the truth of 
this event, in the writings of Lactantius, Dionysius 
of Halicarnassus, and Saint Augustine. 

You have heard the story ; now for superstition. 
" What do you say to that ? " says the superstitious 
Ouintus to his brother Cicero. " You must either 
admit it as a fact, or take refuge in a monstrous 
Pyrrhonism, treat nations and historians as fools, and 
burn their annals. Will you deny everything rather 
than allow that the gods interfere in our affairs ? " 

Hoc ego p kilo sop hi non arbitror testibus uii, qui 



56 DIDEROT S PHILOSOPHICAL WORKS 

aut casu veri aut malitia falsi fictiqiie esse possunt. 
ArgunieJitis et ratio7iibus oportet ; qtiare qtiidquid ita 
sit docere, non eventis, iis prcssertim quibus inihi 
non liceat, credere. . . . Omitte igiturlitumn Ro7nuli^ 
quern in inaximo incendio negas potuisse comburi ? 
Contemne cotem Accii Navii ? Nihil debet esse in 
philosophia commentitiis fabellis loci. Illud erat 
pJiilosophi totius augurii primuni naturani ipsain 
videj'e, delude inventionem^ delude cofistautlaiu. . . . 
Habent Etruscl exaratum puerum auctorem disciplines 
Slice. Nos Queni ? Acclumne Navluui ? . . . Placet 
Igltur huuiaultatls expertes habere Dlvlnltatls auc- 
tores ? (Cicero, De divluat. , lib. ii, cap. Ixxx, Ixxxi). 
But kings, peoples, nations, and the whole world 
believe it. Quasi vere quldquam sit tain valde 
quam nihil sapere vulgare ? Aut quasi tlbl Ipsl In 
judlcando placeat multltudo.^ This is the philo- 
sopher's reply. Tell me a single prodigy to which it 
does not apply. The Fathers of the Church, who 
doubtless found it exceedingly inconvenient to follow 
Cicero's principles, have preferred to accept Tarquin's 
adventure, and attribute the art of Navius to the 
Devil. A very convenient invention, the Devil. 

^ " I think a philosopher ought not to rely on evidence which either 
by accident or design may be false or deceptive. He ought to explain 
by ajgument and reasoning why each circumstance happens as it does, 
rather tlian by events, especially when they are such as I am unable to 
credit. Let us therefore dispose of Romulus's staff, which you say 
resisted the action of the hottest fire, and make light of Navius' flint. 
There should be no place in philosophy for such fabrications. A phil- 
osopher ought to look into the whole matter of augury and its origin. 
The Etruscans set up a boy turned up by a ploughshare as the author 
of their discipline. Whom have we ? Accius Navius ? '' . . . "What 
is commoner than the ignorance of the multitude ? Do you yourself 
trust the common herd in a judicial case?" 



PHILOSOPHIC THOUGHTS 57 

XLVIII 

Every nation has stories like this, which would 
be miraculous if true ; which are never proved, but 
which serve to prove everything ; which it were 
impious to deny, and folly to believe. 

XLIX 

Romulus, struck by lightning, or murdered by the 
senators, disappeared from Rome. The people and 
the soldiers murmured, the orders of the state rose one 
against the other, and Rome in its infancy, divided 
against itself and surrounded by enemies, stood on 
the edge of a precipice, when a certain Proculeius 
came forward gravely, and said : " Romans, this 
prince whom you regret is not dead : he has 
ascended to heaven, where he sits at the right hand 
of Jupiter. 'Go,' he said to me, 'and calm your 
fellow-citizens ; tell them that Romulus is with the 
gods and assure them of my protection ; let them 
know that the forces of their enemies shall never 
prevail against them ; their destiny is to be one day 
the lords of the earth. Let them hand down this 
prediction from age to age, and to their most distant 
posterity.'" Some circumstances favour imposture ; 
and if we consider the state of things in Rome at 
that time, we shall agree that Proculeius was a man 
of intelligence and that he chose his time well, 
lie introduced into their minds a feeling which was 
not without its effect in determining the future 
greatness of his country. Mirum est quanluvi illi 



58 DIDEROT S PHILOSOPHICAL WORKS 

viro h(Fc 7iu7itianti fidei fuerit ; quamque desideriuin 
Roinuli apud plebeni facta fida immortalitatis, 
lenitum sit. Famam hanc admiratio viri et pavor 
prcBsens nobilitavit ; deinde a paucis uiitio facto^ 
Deum, Deo natum salvere U7iiversi Roniuluvi jubent.^ 
That is to say, the people beheved in this appari- 
tion ; the senators pretended to believe, and 
Romulus had altars raised to him. But this was 
not all. Soon it was not only to a single individual 
that Romulus appeared ; he showed himself to 
more than a thousand people in a single day. He 
had not been struck by lightning, the senators had 
not made away with him during a storm, but he had 
ascended to heaven in the midst of lightnings and 
thunders in the sight of the people ; and this story 
became encrusted after a time with such a quantity 
of additions that the thinkers of the following cen- 
tury must have found them highly inconvenient. 



A single proof is more conclusive to me than fifty 
occurrences. Thanks to the great confidence I have 
in my reason, my faith is not at the mercy of the 
first juggler I meet with. Priest of Mahomet, you 
may cure the lame, make the dumb speak, give 
sight to the blind, cure the palsied, and raise the 
dead, nay, even restore to the mutilated the limbs 

1 ["It was strange how the man who announced these tidings was 
beheved, and how the people's longing for Romulus was appeased 
when they believed in his immortality. Admiration of the hero, and 
terror, added lustre to the story ; then, little by little, Romulus is 
hailed as god, and the son of a god, by all."] 



PHILOSOPHIC THOUGHTS 59 

they have lost (a miracle hitherto unattempted), and 
to your great surprise my faith will not be shaken. 
Do you wish me to become your proselyte ? Then 
leave these prodigies and let us reason. I trust my 
judgment more than my eyes. 

If the religion that you announce to me is true, [ 
its truth can be demonstrated by unanswerable 
arguments. Find these arguments. Why pursue 
me with prodigies, when a syllogism serves to con- 
vince me ? Do you find it easier to make a cripple 
stand upright than to enlighten me ? 

LI 

A man lies on the ground, without feeling, 
without warmth and without movement. They 
turn him over and over, shake him, burn him, 
and nothing stirs him. A red-hot iron does not 
draw from him any sign of life. Is he dead ? No. 
He is the priest of Calama, qui qiiando ei placebat 
ad imitatas quasi lamentantis hoininis voces, ita se 
auferebat a sensibus et jacebat siinillinius mortuo, ut 
non solum vellicantes atque pungentes viinime sentiret, 
sed aliquando etiam igne uretur admoto, sine ullo 
doloris sensu nisi post niodum exvulnere.^ I.^-€ €rtain 
people had found such a case in our times, they 
would have made a fine use of him ; we should have 
seen a corpse revived on the ashes of one of the 




^ "Who, when he pleased, became remote from all feeling-antHay 
like a corpse, so that he did not feel those who pinched and pricked 
him, and was even quite insensible to being burnt by fire, except for the 
after effect." — St Augustine, Civit. Dei, lib. xiv, ch. xxiv. 



6o DIDEROT'S PHILOSOPHICAL WORKS 

elect, and the collection of a Jansenist magistrate^ 
would have included a resurrection, and the supporters 
of the famous constitution ^ would perhaps have been 
put to confusion. 

LII 

We must admit, says the logician ' of Port-Royal, 
that Saint Augustine was right in maintaining, with 
Plato, that our judgment of truth and our criterion 
for discerning it belong not to the senses but to the 
mind : noti est veritatis jiidiciiivi in sensibus. And 
even the degree of certainty we can obtain through 
the senses is not very extensive. There are many 
things which we think we learn through their medium 
and of which we have not a full assurance. When, 
therefore, the evidence of the senses is inconsistent 
with, or does not outweigh, the authority of reason, 
we have no choice ; logically, we must decide for 
reason. ~ 

LIII 

A certain street * resounds with acclamations ; 
the ashes of one of the elect ^ work more miracles 

^ La Viiriti des miracles op^ris par rintercession de M. de Pdris, 
d^monirt'e contre M. L'archez'eque de Sens. Onvrage dddii au Roy par 
M. de Montgeron. Utrecht, 1737. There was a continuation in 1741 
and in 174S.— (A) 

- \_I.e. the constitution or Bull Unigenitus, which Louis XIV 
obtained from Clement XI in 17 13. It was an anti-Jansenist measure, 
and was made a law of the land in I730'] 

^ Arnaud and Nicole, in their La Logique, ou r art de pcnser , Amster- 
dam, 1675.— (Br) 

* The faubourg St Marcel, in which stands the Church of St Medard. 

" The Deacon Paris, upon whose tomb the convulsionaries came for 
cures which Carre de Montgeron collected, and which the Jesuits denied 
more passionately and obstinately than the philosophers. — (A) 



PHILOSOPHIC THOUGHTS 6i 

in one day than Jesus Christ during his whole\life. 
Men run', or are carried thither, and I follo\v\the 
multitude. I am no sooner arrived than I hear 
cries of " A miracle, a miracle!" I come nearer, 
and looking about I see a little cripple ^ who wall 
with the aid of three or four charitable persons who"" 
hold him up ; and the people, in astonishment, cry 
out on a miracle. Fools, where is the miracle ? 
Do you not see the rogue has but changed his 
crutches ? It is the same story with miracles as 
with spirits. I would wager that all who have 
seen spirits are afraid of them beforehand, and 
that all those who saw miracles there had made 
up their minds to see them. 

LIV 

VVe have a vast collection ^ of these so-called 
miracles which may bid defiance to the most 
determined incredulity. The author is a senator, 
a serious man who made profession of a not very 
intelligent materialism, but who had nothing to gain 
by his conversion.^ An eye-witness of the events 

' Cripples are of all sick folk the most readily subject to miraculous 
influence, if we are to judge by the enormous number of crutches which 
fill sanctuaries sacred to miraculous cures. In the text the Abbe 
Becheran may be the person referred to ; but he leaped like a carp, 
a detail which Diderot does not give : or Philippe Sergent, stricken by 
a total paralysis of the right leg and thigh, and by almost complete 
paralysis of the right arm and hand ; affected by anchylosis of the knee ; 
affected by a continual tremor in the left side ; and afflicted by imperfect 
sight so that he was only able to see objects dimly, who was cured in a 
single moment of all his maladies at the tomb of the Deacon Paris on 
July loth, 1731.— (A) 

- The collection of Montgeron referred to in note i, page 60. 

•' Montgeron, who makes this confession, had been suddenly converted 
at St Medard, and his conversion is the first miracle he records. —(A) 



62 DIDEROT'S PHILOSOPHICAL WORKS 

which he relates, and which he had the opportunity 
of examining without prejudice or bias, his evidence 
is accompanied by that of thousands of others. All 
say that they have seen, and their depositions are 
as authentic as possible ; the original documents are 
preserved in the public archives. What is to be 
said ? Simply that these miracles prove nothing, 
so long as the question of his boia fides is not 
decided. 

LV 

Every argument which is used by two opposing 
factions cuts both ways. If fanaticism has its 
martyrs like true religion, and if there have been 
fanatics among those who died for the true faith, 
we must either count up (if we can) the number of 
dead of each camp, and believe ; or look for other 
grounds of credibility. 

LVI 

Nothing is more apt to confirm men in their 
irreligion than false inducements to conversion. 
Every day unbelievers are told : " Who are you 
to attack a religion that men such as Paul, TertuUian, 
Athanasius, Chrysostom, Augustine, Cyprian, and 
a host of illustrious persons so courageously 
defended ? Doubtless you have observed some 
difficulty which has escaped these great geniuses ; 
show that you know more than they, or else, if you 
admit that they are the wiser, submit your doubts 
to their verdict." This is a frivolous argument. 



PHILOSOPHIC THOUGHTS 63 

The knowledge of its priests is no proof of the 
truth of a religion. What faith was more absurd 
than the Egyptians ? And what priesthood was 
more enlightened? "No, I cannot worship this 
onion ; in what is it superior to other vegetables ? 
I should be mad indeed to bow down before objects 
destined for my nourishment ! A strange divinity, 
a plant that 1 water, and which grows and dies in 
my kitchen garden." "Silence, you wretch, your 
blasphemies fill me with horror. Who are you to 
argue ? Do you know more than the sacred college ? 
Who are you to attack the gods, and preach wisdom 
to their ministers ? Are you wiser than the oracles 
that the whole world comes to question ? Whatever 
your answer, I shall be amazed at your pride and 
temerity ! " Will Christians never know their 
strength, and will they never abandon such unhappy 
sophisms to those who have no better argument ? 
Omittamur ista cojuDiunia qiicB ex utraque parte 
did possunt, quanquam vei-e ex utraque parte did 
non possint.^ Example, prodigies and authority ^ 
may make dupes or hypocrites ; reason alone can J ^ 
make be lievers. 
' LVIl 

People agree that it is of the first importance to 
employ none but solid arguments for the defence of 
a faith ; yet they would gladly persecute those who 
attempt to cry down bad arguments. What, then, 
is it not enough to be a Christian ? Am I also to 

' [" Let us leave all these common arguments which may be used by 
either party, although really they cannot be used by either. "J 



64 DIDEROT'S PHILOSOPHICAL WORKS 

be a Christian upon mistaken grounds ? Zealots, I 
give you fair warning, 1 am not a Christian because 
Saint Augustine was, but because it is reason- 
able to be one. 

LVIII 

I know the zealots well, and they are quick to 
take alarm. If they once make up their .minds 
that this work contains something repugnant to 
their ideas, I shall expect all the calumnies they 
have spread about a hundred better men than 
myself. If they only call me a deist and a wretch, | 
I shall get off lightly. They have long since 
damned Descartes, Montaigne, Locke and Bayle ; 
and I hope that they will damn many others. ^I 
tell them that I do not pretend to be a better^ 
man nor a better Christian than most of these 
philosophers. I was born in the Roman, Catholic, 
and Apostolic Church, and I whole-heartedly submit 
to its decisions. I wish to die in the faith of my 
fathers, and I respect it as far as is possible for a 
man who has never held immediate intercourse with 
the Deity, and has never witnessed a miracle. That 
is my confession of faith, and I am persuaded that 
they will find fault with it, though perhaps not a 
man among them can make a better. 

LIX 

I have occasionally read Abbadie, Huet,^ and 
the rest. I am sufficiently well acquainted with the 

1 Abbadie, Traiti de la vi^riti de la religion chrMemie, 172;. Huet, 
Traiti philosophique de la faiblesse de Pesprii huinairie, 1723. — (A) 



PHILOSOPHIC PHOUGHTS 65 

evidences of my religion, and I admit that they are 
important ; but were they a hundred times more so, 
Christianity would not be demonstrated to me to / 
be true. Why then demand that I should believe 
that there are three Persons in one God as firmly 
as 1 believe that the three angles of a triangle are 
together equal to two right angles ? Every proof 
ought to produce in me a certainty proportionate 
to its conclusiveness, and the effect of geometrical, 
moral and physical proofs upon my mind must be 
different, or else this distinction is a frivolous one. 

LX 

You offer an unbeliever a volume of writings of 
which you claim to show him the divinity. But 
before examining your proofs, he will be sure to 
put some questions about this collection. Has it 
always been the same ? Why is it less ample now 
than it was some centuries ago ? By what right 
has this or that work been banished, which another 
sect reveres ; and this or that work been preserved, 
which the other has rejected ? On what grounds 
have you preferred this manuscript ? Who guided 
you in your choice among so many varying copies, 
which are a proof that these sacred authors have 
not come down to you in their original purity ? 
But if the ignorance of copyists or the malice of 
heretics has corrupted the text, as you will have to 
admit, you mu.st restore the text to its original 
condition before you prove its divinity ; for your 
proofs and my faith cannot rest upon a collection 

5 



66 DJDEKOTS PHILOSOPHICAL WORKS 

of mutilated documents. To whom will you entrust 
this reform ? The Church. But I cannot agree to 
the infallibility of the Church, until the divinity of 
the Scriptures is proved, I am therefore reduced 
to scepticism. 

Your only answer to all these difficulties is by 
the confession that the first Ibundation s of th e faith 
are purely human ; that the choice between manu- 
scripts, the restoration of passages, finally the 
collection, has been made in accordance with the 
rules of criticism. Well, I do not refuse the divinity 
of the sacred books a degree of faith proportioned 
to the certainty of these rules. 

LXI 

It was during my search for proofs that 1 found 
difficulties. The books which contain the motives 
of my belief offer at the same time inducements 
to unbelief. They are arsenals from which either 
party may draw weapons. I have seen the deist 
arm himself there against the atheist ; the deist and 
the atheist attack the Jew ; the atheist, the deist 
and the Jew combine against the Christian ; the 
Christian, the deist, the atheist and the Jew oppose 
the Mussulman ; the atheist, the deist, the Jew, and 
the Mussulman, and a multitude of Christian sects, 
attack the Christian ; and the sceptic with his hand 
against every man. I was the umpire, and held 
the balance between the adversaries. It rose or 
fell in sympathy with the weight thrown into the 
scales. After long hesitation, the balance dipped 



PHILOSOPHIC THOUGHTS 6y 

in fcavour of the Christian, but simply by way of 
reaction. I can bear witness to my own impartial- 
ity. 1 mi!j;ht ha\e made more of this surplus. 1 
call God to witness my sincerity. 

LXII 

This diversity of (opinions has led the deists to 
imagine an argument which is perhaps more curious 
than solid. Cicero, having to prove that the Romans 
were the most warlike people in the world, skilfully 
extracts this admission from the lips of their rivals. 
Gauls, to whom, if any, do you yield the palm in 
courage? To the Romans. Parthians, after you, who 
are the bravest of men ? The Romans. Africans, 
whom would you fear, if you were to fear any ? 
The Romans. Let us, say the deists, interrogate 
the religionists in a like manner. Chinese, what 
religion would be the best, if yours were not the 
best ? Naturalism. Mussulmans, what religion 
would you embrace if you abjured Mahomet ? 
Naturalism. Christians, what is the true religion 
if it be not Christianity ? Judaism. But you, O 
Jews, what is the true religion, if Judaism be false ? 
XaiiiraJism^ Now, those, continues Cicero, to whom 
the second place is unanimously awarded and who 
in their turn do not cede the first place to anyone 
— it is those who incontestably deserve that place. 



LETTER ON THE BLIND FOR THE 
USE OF THOSE WHO SEE ^ 

Possunt nee posse videntur. — ^-Jiueid, lib. v, 23.'^ 

It was not more than I suspected, that the bhnd 
girl whom Monsieur de Reaumur had couched for 
cataract would not inform you of what you were 
anxious to know ; but I little thought it would be 
neither her fault nor yours. I have in person, and 
by means of his best friends and by paying him 
man)- compliments, applied to her benefactor, but 
all in vain ; the nrst dressing will be removed with- 
out you. Some persons of the highest distinction 
have had the honour of sharing this refusal with 
philosophers, and, in a word, he does not wish to - | 
remove the veil, except in the presence of some eye- J 
witnesses of no great importance. If you would 
know why that wonderful operator makes a secret 
of experiments at which you think too great a 
number of intelligent witnesses cannot be present, 
my answer is, that the observations of such a cele- 
brated person do not so much stand in need of 
spectators, whilst making, as of hearers when made. 

^ The Letter was addressed to Madame de Puisieux. — (A) 
" [The original is : Possunt quia possunt videntttr — "They succeed 
because they think they will succeed.'"] 

68 



THE LETTER ON THE BLIND 69 

Thus, disappointed, madam, I have returned to my 
original intention, and, since I was forced to go 
without an experiment in which I saw little profit 
would accrue to you or to me, but of which Monsieur 
de Reaumur will doubtless make a much better use, 
I set to work to philosophise with my friends upon 
the important matter which is the object of it. How 
happy should I be, if the narrative of one of our 
conversations might stand instead of the spectacle 
1 so rashly promised you ! The day that the 
Prussian^ operated on Simoneau's daughter for 
cataract, we went to have some talk with the 
Puisaux ^ man who was born blind. He is possessed 
of good solid sense, is known to great numbers of 
persons, understands a little chemistry, and has 
attended the botanical lectures at the Jardin du Roi 
with some profit to himself. His father was a 
distinguished professor of philosophy at the Univer- 
sity of Paris. He had private means, sufficient to 
have satisfied his remaining senses, but a taste for 
pleasure led him into some excesses in his youth ; 
people took advantage of his weaknesses, his affairs 
became embarrassed, and finally he withdrew to a 
little town in the provinces, from whence he pays 
a yearly visit to Paris, bringing with him liqueurs 
which give great satisfaction. These, madam, are 
not very philosophic details, but for that very reason 
are likely to convince you that the person 1 am 
speaking of is not imaginary. 

' Ililmer, a Prussian oculist. — (Br) 
'^ A small town in the G.-itinais. — (D) 



70 DIDEROT S PHILOSOPHICAL WORKS 

We arrived at our blind man's house about five 
o'clock in the afternoon, and we found him busy 
teaching his son to read with raised letters. He 
had only been up an hour, for I must tell you the 
day begins for him when it is ending for us. His 
custom is to look after his household affairs and to 
work wdiile others are asleep. At midnight nothing 
interrupts him, and he is in no one's way. His 
first care is to set in its place everything that has 
been displaced during the day, and when his wife 
wakes she generally finds the house tid\'. The 
[ difficulty the blind have in finding things that are 
i\ mislaid makes them orderly, and I have observed 
I that their intimates also share this quality, either 
from the effect of the good example of the blind, or 
from a feeling of compassion towards them. How 
unhappy would the blind be without the little 
attentions of those about them ! — nay, we ourselves 
feel the want of them. Great services are like the 
large gold or silver coins that we rarely make use 
of, but small attentions are small change which is 
always passing from hand to hand. 

This blind man is a good judge of symmetry. 
Symmetry, which is perhaps a matter of pure con- 
vention among us, is certainly so in many respects 
between a blind man and the sighted. A blind 
man studies by his touch that disposition required 
between the parts of a whole to enable it to be called 
beautiful ; and then at length attains to a just 
application of that term. But in saying "that Is 
beautiful," he does not form an opinion, it is no 



THE LETTER ON THE BLIND yi 

more than repeating the judgment of those who see ; 
and is not this the case of three-fourths of those 
who give their opinion on a pla}' or a book ? Beauty 
for the blind is but a word when divorced from 
utility, and, wanting an organ, how many things 
are there the utility of which escapes them ? Are 
riot the blind very much to be pitied in accounting 
nothing beautiful unless it be likewise good ? How 
rhany admirable things are lost to them ! The only 
compensation for their loss is that their ideas of ( 
beauty, though less extensive, are more definite 
than those of many keen-sighted philosophers Avho ' 
have written prolix treatises on the subject. This 
blind man often speaks of mirrors. You think he 
does not know the meaning of the word, yet he is 
never known to put a glass in a wrong light. He ^ 
speaks as sensibly as we on the qualities and defects 
of the organ which he lacks. If he attaches no idea'} 
to the terms he makes use of, yet he has the! 
advantage over most other men that he never uses 
them wrongly. He speaks so wisely and so well of 
so many things absolutely unknown to him, that his 
conversation would considerably lessen the weight 
of that inference which, without knowing wherefore, 
we all draw from what passes in ourselves to what 
passes within the minds of others. 

I asked him what he meant by a mirror? " An 

instrument," answered he, "which sets things in 

relief at a distance from themselves, when properly 

"placed with regard to it. It is like my hand, which, 

to feel an object, I must not put on one side of it." 



72 DIDEROT S PHILOSOPHICAL WORKS 



/ - 



b 



Had Descartes been born blind, he might, I think, 
have hugged himself for such a definition. Pray 
consider what an ingenious combination of ideas 
it implies. This blind man's only knowledge of 
objects is by touch. He knows by hearing other men 
say so that they know objects by sight as he knows 
them by touch ; at any rate that is the only idea he 
can form of the process, vjie also knows that we 
cannot see our own face though we can touch it. 
Sight, he therefore concludes, is a kind of jtouch 
^'hich extends to distant objects and is not applied 
to our face. Touch gives him an idea only of relief. 
Therefore, he concludes, a mirror is an instrument 
that represents us in relief outside ourselves. How 
many famous philosophers have laboured with less 
subtlety to arrive at conclusions equally erroneous ! 
But if a mirror astonished our blind man, how much 
greater was his surprise when we told him that there 
are instruments which magnify objects, while others 
remove them without duplicating them, put them 
out of their place, bring them nearer, remove them 
farther, and reveal the minutest details to the eyes 
of naturalists ; while others again multiply objects 
a thousand times, and others appear to change the 
figure of objects completely. He asked us a hundred 
curious questions concerning these phenomena. For 
instance, he asked us if onl}^ persons who were called 
naturalists could see with the microscope, and if 
only astronomers could see with the telescope ; if 
the instrument for enlarging objects were bigger 
than that for diminishing them ; if that which brings 



THE LETTER ON THE BLIND 71 

them nearer were shorter than that for removing 
them farther off. l^it what puzzled him was that 
the other self, which according to him the mirror 
represents in relief, should not be tactile. 

"So this little instrument," said he, "sets two 
senses to contradict one another ; a more perfect 
instrument would perhaps reconcile these contradic- 
tions, without the object being ever more real for 
that, and perhaps a third instrument, still more 
j[)crfect and less illusory, would cause these contra- 
dictions to disappear and show us our error." 

"And what are eyes, do you suppose?" asked 

Monsieur de . "An organ," replied the blind 

man, " on which the air has the effect this stick has 
on my hand." That answer amazed us, and while 
we gazed at one another in astonishment he con- 
tinued : "When I place my hand between your 
eyes and an object, my hand is present to you but 
the o"bject is absent. The same thing happens 
when I reacli for one tiling \\\\\y my stick and come 
across another." 

I^Tadam, only turn to Descartes' Dioptrics, and 
there you will see the phenomena of sight illus- 
trated by tho.se of touch, and the plates full of men 
busied in seeing with sticks. Descartes, and all 
the later writers, have not been able to give us 
clearer ideas of vision ; and that great philosopher 
was, in this respect, no more sujjcrior to the blind 
man than a common man who has the use of his 
eyes. 

No one thought of asking him ([uestions as to 



74 DIDEROT S PHILOSOPHICAL WORKS 




Fig. I. 



The above figure is an enlarged reproduction of the cut in the 
original edition of the Letter on the Blind. In the Discotirs dc la 
nuHhode, plus la dioptriqiie, les nuUt'ores, la vt^canisme ct la musiqtte 
(Leyden, 1637), blind people trying to see with sticks are often repeated, 
but these are small figures only an inch in height dressed as beggars 
and accompanied by a dog. Diderot probably refers to an edition by 
P. N. Poisson of this work (1724). — (A) 



THE LETTER ON THE BLIND 75 

pajn+.ncT and writing, but it is obvious that his 
compoli-lsou would fit in with every question, and I 
malce no doubt but that he would have told us that 
to try to read or to see without eyes was like looking 
for a pin with a thick stick. We only talked to him 
a^ouXthose kinds of glasses which exhibit objects in 
r elief,_ aiid which are both so very similar to and so 
very different from mirrors ; but these we perceived 
rather contradicted than coincided with his idea of a 
looking-glass, and he was apt to think that a painter 
might perhaps paint a looking-glass, and thus it 
came to represent objects in colours. 

Wesaw him thread very fine needles. May I ask 
you, madam, to suspend your reading for a while 
and try what you would do in his place? In case 
you do not light upon any expedient, I will tell you 
of our blind man's. He takes the eye of the needle 
transversely between his lips and in the same direc- 
tion as his mouth, then by his tongue and suction 
he draws in the thread, which follows his breath 
unless it is much too thick for the eye ; but in that 
case a man with sight is in the same difficulty as 
the blind. 

He has a surprising memory for sounds, and can 
distinguish as many differences in voices as we can 
in faces. He finds in these an infinite number of 
delicate gradations which escape us because we have 
not the same^nterest in observing them. For us, 
these~sTiacIes oT difference are like our own counten- 
ance. Of all the men we have seen, the one we 
least remember is our own self. We notice faces to 



id DIDEROT S PHILOSOPHICAL WO 

recognise people ; and if we do not rememb«ry jur 
own, it is because we are never liable to m jtake 
ourselves for another person or another for our- 
selves. Moreover, the mutual aid our senses lend 
stands in the way of their perfection. This will not 
be the only occasion where I shall have to remark 
upon this. 

On this head our blind man said: "That he 
should think himself a pitiable object in_i\Lanting 
those advantages which we enjoy, and that he should 
have been inclined to consider us as superior beings 
I had he not a hundred times found us very much 
inferior to him in other respects." This reflection 
led to another. This blind man, we said, values 
himself as much as, and perhaps more than, vve 
who see. Why then, if the brute reasons (and 
it is scarce to be doubted), why on weighing its 
advantages over man as better known to it than 
those of man over it, should it not make a similar 
inference ? He has arms, perhaps says the gnat, but 
I have wings. He has weapons, says the lion, but 
have we not claws ? The elephant would look on 
us as insects ; and all the animals, while allowing 
us reason, with which we should at the same time 
stand in great need of their instinct, would claim 
that with their instinct they could do very well with- 
out our reason. We have such a strong desire to 
exaggerate our qualities, and make little of our 
defects, that it would seem man's part to write a 
treatise on force, and animals' on reason. 

One of our company bethought him of asking our 



THE LETTER ON THE BLIND 77 

hmd man if he would like to have eyes. "If it ^y\ 
weie not for curiosity," he replied, " I would just as 
sooi have long arms : it seems to me my hands 
would tell me more of what goes on in the moon 
than your eyes or your telescopes ; and besides, eyes 
cease to see sooner than hands to touch. I would 
be as well off if I perfected the organ I possess, as ) 
if 1 obtained the organ which I am deprived of." 

Our blind man points with such exactness at the 
place; whence a noise comes that I make no doubt 
the D|lind may, by practice, become very dexterous 
and very dangerous. I will tell you a story which 
vvITl convince you how imprudent it would be to 
stand the throwing of a stone or discharging of a 
pistol b)' a blind man, were he in the least used to 
that weapon. He had in his youth a quarrel with 
one of hin brothers, who came off badly. Provoked 
at some insulting language, he seized the first missile 
which caime to hand, threw it at him, and hit 
him directly on the forehead, so as to lay him flat 
on the ground. 

This, with some other occurrences of the like 
kind, caused him to be brought before the police.-^]^ 
The outward show of power, which affects us so' 
strongly, is as nothing to the blind. Our blind 
man appeared before the magistrate, as before an 
equal; menaces did not intimidate him. "What 
will you dcj to me?" he asked Monsieur Herault.^ 
"I will commit you to a dungeon," answered the 
magistrateT^""^' Ah, sir," the blind man replied, "1 

' Lieultiuant of police. — (Br) 



/ 



78 DIDEROTS PHILOSOPHICAL WORKS 

have been in one for twenty-five years. " There vas 
an answer, madam ; and what a text for one who is so 
fond of morahsing as your humble servant ! We quit 
life as we would a charming scene, the blind lea*^e it 
as a dungeon ; and if we have more pleasure in living 
than he, he has less reluctance to meet his end. 

The blind man of Puisaux judges of his nearness 
to the fire by the degrees of heat ; of the fuln^^^- ^^ 
vessels by the sound made by liquids whic 4- 
pours into them ; of the proximity of bodies by the 
action of the air on his face. He is so sensithve to 
>/.. the least atmospheric change, that he can diiiiilguish 
between a street and a closed alley. He is an 
extremely good judge of the weight of bodies and 
the capacity of vessels ; and he has trained his arms 
to be such an exact| balance, his fingers to' be such 
skilful compasses, that in this kind of statics I 
would always back our blind man ^ against twenty 
persons with all their eyes about them. ■, The 
smooth surface of bodies has as many shades of 
difference for him as the sound of voices, and there 
is no risk of his mistaking his wife for another, 
unless he was to be the gainer by the change. Yet 
it is very probable that among a blind people^wjves 
would be in common, or their laws against adultery 
must be severe indeed, so very easy woiddJt.be for 
wives to deceive their husbands by concerting a 
sign with their gallants. 

^ Clemenl {Citiq ann^es littdraires, lettre xxx'ii) chooses this 

passage to give his correspondent some idea of tiis new book of 

Diderot's which he describes as obscure, and in which he only finds a 
very slight exhibition of learning.— (A) 



THE LETTER ON THE BLIND 79 

He judges ol beaut)- b)' touch — that is easy to 
understand ; but what is not so easy to grasp is 
that his judgment is influenced by pronunciation 
and the sound of a voice. Anatomists ought to tell 
"uFif there is any relation between the parts of the 
mouth and the palate and the exterior conformation 
of the face. He can turn small articles on the lathe, 
and do needlework ; he levels with a square ; he 
puts together and takes to pieces simple machines. 
He is so far skilled in music as to play a piece when 
he has been told the notes and their value. He 
judges of the duration of time much more accurately 
than we by the succession of actions and of thoughts. 
A smooth skin, firm flesh, an elegant shape, sweet 
breath, charm of voice and graceful pronunciation 
are qualities he prizes very highly. 

He married to have eyes of his own. Iiefore 
this, he had an idea of taking a deaf man as his 
partner, to whom he could lend ears in exchange 
for ej'es. I could not sufficiently wonder at his 
singular address in a great many things ; and on our 
expressing our surprise, " 1 perceive, gentlemen," 
said he, " that you are not blind : you are astonished 
at what I do, and why not as much at my speak- 
ing ? " There is more philosophy, I believe, in this 
a nswer o f his than he was aware of. The facilit}' 
with which we are brought to speak is not a little 
surprising. We have a number of ideas which 
cannot be represented by sensible "objects, and 
which have no substance, as it were, and we are 
obliged to find terms for them by making use of a 



8o DiDEROrS PHILOSOPHICAL WORKS 

number of ingenious and profound analogies observed 
between them and the ideas they suggest. Thus a 
Wind man should find greater difficulty in learning 
to speak because there is a much larger number 
of imperceptible objects in his world, and thus 
his field for comparing and combining is much more 
limited. How, for example, can he rightly use 
the word expression (of countenance) ? It is the 

y^^same of many things imperceptible to the blind ; 
y and for us who see, it is often found hard to explain 
very precisely what it is. If it largely resides in 
%^ the eye, touch will be useless ; and what does a 
^ blind man make of dead eyes, or sparkling or 
^ expressive eyes ? I infer from thence that we 
unquestionably derive great__adyantages from the 
concurrence of oiir "senses and our organs; still, it 
would ^be quite anbtlier Tiling did we use them 
separately, and never employed two when one 
would suffice. To add touch to sight, when sight 
would do the business, is like putting to a carriage 
with two stout horses a third, which will draw one 
way while the others draw another. 

As to me it has always been very clear that the 
state of our organs and our senses has a_ great 
influence on our metaphysics and our morality, and 
that those ideas which seem purely intellectual are 
closely dependent on the conformation of our 
bodies, I put some questions to the blind man 
about the virtues and vices. The first thing I 
remarked was his extreme abhorrence of Jjie^ 
possibly from two reasons — firstly, the facility with 



THE LETTER ON THE BLIND 81 

which people could steal from him unobserved, and 
secondly (and still more perhaps), because he could 
be^Jmmediately seen were he to go about filching. 
Not that he is at any loss to secure himself against 
that sense which he knows we have above him, or 
that he is clumsy at hiding what he might steal. 
Mode sty he makes no great account of. If it were -^ — 1 
not for the weather, against which clothes are a 
protection, he would hardly understand their use ; 
and he openly admits he cannot see wh)' one part 
of the body should be hidden rather than another ; 
and still less by what caprice some of those parts 
should be especially singled out, which from their 
use and the indispositions to which they are subject j 
ou^ht rather to be kept free. Though living in an 
age when philosophy has rid us of a great number 
of prejudices, I do not think we shall ever arrive at 
su<ph complete insensibility to the prerogatives of 
mcjdesty as this blind man. Diogenes would have 
been no philosopher in his account. 

As of all the external signs which raise our pity 
ai|id ideas of pain the blind are affected only by cries, ' 1 
I^^have in general no high thought of their humanityT^ />^ — 
VVhat difference is there to a blind man between a man 
niaking water and one bleeding in silence? Do not we 
ojurselves cease to be compassionate when distance or 
t.he smallness of the objects produces on us the same 
etffect as deprivation of sight upon the blind ? So 
trju^ch do our virtues depend on the sensations we 
n^eiye, and the degree by which we are affected by 
external things. ^ I don't doubt that if it were not 
' V, ^ 6 



/ 



c 



82 DIDEROT'S PHILOSOPHICAL IVCkKS 

for the fear of punishment, many people wouhi-find it 
less disagreeable to kill a man at a distailce at which 
he would appear no bigger than a swallow, than to 
cut an ox's throat with their own hands. We pity 
a horse in pain, and we make nothing of crushing 
I an ant ; and is it not by the same principle that we 

rare moved? Ah, madam, how different i« tfceimor- 
ality of the blind from ours ? How different Would 
that of a deaf man likewise be from his ? Aiid to 
one with a sense more than we have, how deficient 
would our morality appear — to say nothing rAcire ? 
Our metaphysics and theirs agree no better. How 
many of their principles are mere absurdities to us, 
I and vice versa ? Concerning this I might enter i nto 
details, which I am pretty certain would amuse you, 
but which certain people, who make a crime of eve ry- 
thing, would not fail to exclaim against as profanity 
and infidelity, as if it were in my power to make the 
blind perceive things otherwise than they do. I w ill 
content myself with one observation, which every- 
one must allow, and that is, that the great arg4ime"nt 
for the wonders of nature falls flat upon the blinJJ. 
Tlie facility with which we create (if I -may say sp) 
new objects by means of a little glass, tS so nethinlg 
more incomprehensible to them than the stars whiqh 
they have been condemned never to . see. ThUs 
luminous globe which moves from east to west sur - 
[^ /' prises them less than a small fire which thm^ can 
>^ increase or diminish at will ; and as they see ma^*:e.r 
^ in a more abstract manner than we do, they are \62is 
indisposed to believe that it thinks. 



THE LETTER ON THE BLIND 83 

If a man who had had sight only for a day or 
two found himself in the midst of a blind people, 
he would either have to hold his peace or be con- 
sidered a brain-sick fool. , Every day he would 

come out with some new wonder, which would only 
be such to them, and which their free-thinkers 
would oppose tooth and nail. Might not the apolo- 
gists of religion greatly avail themselves of such a 
stubborn unbelief^ which, however just in some 
respects, is yet so very ill-founded ? Be pleased to 
dwell only a little upon this supposition ; it will 
remind you of the persecutions undergone by those 
poor wretches who .discovered truth in the dark ages 
and were rash enough to reveal it to their blind v 
contemporaries, and found their bitterest enemies 
\vere those who from their circumstances and educa- 
tion would have seemed most likely to receive it 
willingly. 

So much for the morals and metaph) sics of the 
blind. I now pass on to less important matters, 
which have nevertheless lately been the chief subject 
of observation with regard to the blind ever since 
the Prussian oculist's arrival. First question : How sX, 
can a man born blind form ideas of figures ? By 
the movements of his own body and by stretching 
his hand in various directions, by passing his fingers 
continuously over an object, he get s an idea ot space. 
If he passes his fingers along a taut thread, he 
obtains the idea of a straight line ; if he follows the 
curve of a slack thread, that of a curve. In a more 
general sense, by repeated usage of the sense of 



84 DIDEROT'S PHILOSOPHICAL WORKS 

touch, he has a memory of sensations experienced 
at different points ; and he is capable of combining 
these sensations or points and forming figures. A 
straight Hne for a bhnd man who is not a geomet- 
rician is but the memory of a series of sensations 
of touch upon a taut thread ; a curve, the memory 
of a series of tactile sensations referred to the surface 
of some concave or convex solid. In the case of a 
geometrician, study corrects the idea of these lines 
by their properties which he discovers. But whether 
geometrician or no/the man born blind refers every- 
thing to his fingers' ends. We combine coloured 
points, he only palpable points, or, to s^gaj^ more 
precisely, only such tactile sensation^j.'^ he remem- 
bers. He does not go through a mental process 
analogous to ours ; he does not create an image, for 
to do this it is necessary to colour a background and 
mark upon it points of a different colour from that 
background. Make these points of the same colour 
as the ground, and they are at once lost in it, and 
the figure disappears ; at any rate, that is the case 
in my imagination, and I suppose all imaginations 
are alike. When I propose to perceive in my head 
a straight line otherwise than by its properties, I 
begin by spreading in it a white cloth, against which 
I set out a series of black points in the like direction. 
The stronger the colour of the ground and points, 
the clearer my perception of the points. To view 
in my imagination a figure of a colour resembling 
that of the ground, puts me to no less trouble than 
if out of myself and on a canvas. You see then, 



THE LETTER ON THE BLIND 85 

madam, that laws might be given for imagining with 
ease various objects variously coloured, but such 
laws are by no means calculated for one born blind. 
Such_ a. man who cannot colour (and consequently _j 
cannot figure as we understand it) only remembers 
such sensation as one derives from touch, which 
he refers to different points, places and distances, 
and of whic h he compose s figures. I believe that 
we who see never imagine any shape without colour- j 
ing it, and that if we are given little balls in the ■"* 
dark, whose substance and colour are unknown to 
us, we shall immediately think of them as black or 
white, or some other colour ; and that if we did not, 
we, like the blind man, should have the remembrance 
only of little sensations excited at our fingers' ends, 
and such as little round bodies may occasion. If 
this remembrance be very fleeting with us, if we 
have very little idea how one born blind fixes, 
recalls and combines the sensations of touch, it is 
owing to the custom we derive from our eyes of -r 
realising everything in our imagination by means of J 
coloiirSi.-. It has happened, however, that during 
the agitations of a violent passion I felt a thrill 
run through my whole hand, and I felt the im- 
pression of the bodies I had touched some time ago 
rcvi\*„vl as vividly as if they had been still jirescnt 
to my touch, and I realised ver}' distinctly that the 
limits of sensation exactly coincided with th_osc of 
these absent bodies. Although sensation by itself ^ 
is indi\isiblc, it occupies, if one may use the word, 
an extension in space to which the blind man is 



./ 



86 DIDEROT S PHILOSOPHICAL WORKS 

able to add and subtract mentally by enlarging or 
diminishing the parts affected. By this means he 
compares points, surfaces, and solids ; and he could 
imagine a solid as large as this terrestrial globe, if 
he were to imagine his fingers' ends as large as this 
globe, and occupied by sensation in its length, 
breadth, and depth. I know of nothing which is 
a better proof of the reality of this internal sense 
than this faculty, weak in us, but strong in those 
born blind, of feeling or recalling the sensation of 
bodies when they are absent and no longer acting 
on us. We cannot make a blind man understand 
how imagination represents absent objects as present 
to us, but we can easily recognise in ourselves the 
faculty that the blind possess of feeling at one's 
fingers* ends an absent body. To do this, press 
the forefinger and thumb together, shut your eyes ; 
separate your fingers, and immediately after this 
separation examine yourself and tell me if the 
sensation does not linger after the pressure has 
ceased ; if, while the pressure lasted, your mind 
appears to be in your head rather than at the ends 
of your fingers, and if this pressure does not convey 
the nature of a surface by the space v^hich the 
sensation occupies ? We only distinguish the 
presence of external things from their pic^^i're in 
our imagination by the strength or weakness of the 
impression ; and similarly, the blind only distinguish 
the sensation from the actual presence of an object 
at their fingers' ends, by the strength or weakness 
of that sensation. 



THE LETTER ON THE BLIND 87 

If ever a philosopher, blind and deaf from his 
birth, were to construct a man after the fashion 
of Descartes, I can assure you, madam, that he 
would put the seat of the soul at the fingers' ends, 
foL. thence the greater part of the sensations and all 
his knowledge are derived. Who is to inform him 
that his head is the seat of his thoughts? If the 
labours of the imagination tire our brain, this is 
because the effort we make to imagine is somewhat 
si milar to that to perceive very near or very small 
objects. But this would not be the case with a man 
blind and deaf from his birth, for the sensations 
which he.lias_gathered from touch will be the world, 
so to s peak, of all his ideas, and I should not be 
^rprised if, after a profound meditation, his fingers 
were as wearied as our heads. I am not afraid that 
a philosopher might object to such an one that the 
nerves cause our sensations and that they all start 
from the brain. Were these two propositions fully 
demonstrated, which is very far from being the case, 
especially the former, an exposition of all the dreams 
of naturalists on this head would be sufficient to 
confirm him in his opinion. 

But if the Jrnagination of the blind man be no 
fQore^than the faculty of calling to mind and com- 
bining sensations of palpable points ; and of a sighted 
rnari^, the faculty of combining and calling to mind 
visible or coloured points, the person born blind 
consequently perceives things in a much more 
abstract manner than we ; and in questions purely 
speculative, he is perhaps less liable to be deceived. 



88 DIDEROTS PHILOSOPHICAL WORKS 

For abstraction consists in separating in thought 
the perceptible quahties of a body, cither from one 
another, or from the body itself in which they are 
inherent ; and error arises where this separation is 
done in a wrong way or at a wrong time — in a wrong 
way in metaphysical questions, or at a wrong time 
in applied mathematics. There is perhaps one certain 
method of falling into error in metaphysics, and that 
is, not sufficiently to simplify the subject under in- 
vestigation ; and an infallible secret for obtaining 
incorrect results in applied mathematics is to suppose 
objects less compounded than they usually are. 

There is one kind of abstraction of which so few 
are capable that it seems reserved for purely intel- 
lectual beings, and that is that by which ever)'thing 
would be reduced to numerical units. We must 
admit that the results of this geometry would be 
very exact, and its formulas very comprehensive, 
for there are no objects, either possible or actually 
existent, which these simple units could not represent, 
by points, lines, surfaces, solids, thoughts, ideas, 
sensations, etc. ; and if this should prove to be the 
foundation of Pythagoras's doctrine, he might be 
said to have failed in his aim, his mode of philoso- 
phising being too much above us, and too near that 
of the Supreme Being, who, according to the in- 
genious phrase of an English geometrician,^ always 
geometrises in the universe. 

^ [Bricre gives the name of this geometrician as Rapson [sic). Raphson, 
not a very distinguished mathematician, may, among many others, have 
quoted this doctrine of Plato, but it is not very important .-f he did so. 
What makes the diclum important in Plato's mouth is that he had a 



THE LETTER ON THE BLIND 89 

But units pure and simple are too vague and 
general symbols for us. Our senses bring us back 
to symbols more suited to our comprehension and 
the conformation of our organs. We have arranged 
that these signs should be common property and 
serve, as it were, for the staple in the exchange 
of our ideas. We have made them for our eyes in ' 
the alphabet, and for our ears in articulate sounds ; 
but we have none for the sense of touch, although 
there is a way of speaking to this sense and of 
obtaining its responses. For lack of this language, 
there is no communication between us and those 
horn deaf, blind, and mute. They grow, but the}' 
remain in a condition of mental imbecility. Perhaps 
they would have ideas, if we were to communicate 
with them in a definite and uniform manner from 
their infancy ; for instance, if we were to trace on 
their hands the same letters we trace on paper, and 
associated always the same meaning with them. 

Is not this language, madam, as good as another? 
Is it not ready to hand, and would you dare to say 
that you have never been communicated with b)- 
this method f Nothing remains but to fix it, and 
make its grammar and dictionaries, if it is found 
that the expression by the common characters of 
writing is too slow for the sense of touch. Know- 
ledge has three entrances by which it reaches our 

theory that jjcometry is more fundamental and comprehensive than 
arithinetic. He disay;reed in this respect from the I'ythagoreans because 
he clearly realised thai there were certain lengths of lines expressible 
geometrically but not arithmetically; cf. Brunschvicg, Les dtapes dc la 
philosophie nia/ht*r>iaO'(/iir, pp. 45, 47, 4S. ] 



90 DIDEROT S PHILOSOPHICAL WORKS 

mind, and we keep one barricaded for want of signs. 
If the two others had been neglected we should now 
be little better than beasts. Just as a pressure is 
the only sign we have to the touch, so a cry would 
have been the only sign to the hearing. We have 

^> to lose one sense before we realise the advantage of 
symbols given to the remainder, and people who 
have the misfortune to be born deaf, blind, and mute, 
or who have lost these three senses by some accident, 
would be delighted if there existed a clear and 
precise', language of touch. 

^ It is much easier to use symbols already invented 
than to invent them, as one is obliged to do when 
there are none current. What an advantage it would 
have been for Saunderson to find an arithmetic 
arranged with signs for the touch all ready to hand 
at the age of five, instead of having to invent it at 
twenty-five ! This Saunderson, madam, is another 
blind man whose story you will be interested to 
hear. Wonderful stories, indeed, are told of him, 
and yet there is not one to which, from his attain- 

\/ ments in literature and his skill in mathematics, we 
may not safely give credit. He used the same 
machine for algebraical calculations and for the 
description of rectilinear figures.' You_would be 
interested in an account of this if intelligible, and 
you will see my description assumes no more know- 
ledge on your part than you actually possess, and 
that it would be very useful to you if )'ou should 
ever want to make long calculations by touch. 

' See note i, p. i\^. 



THE LETTER ON THE BLIND 91 

Imagine a square such as you see in figures 2 and 

3, divided into four equal parts by lines perpendicular 
to the sides, in such a way that it gives nine points, 
i» 2, 3, 4, 5, 6, 7, 8, 9. Suppose this square per- 
forated with nine holes to hold pins of two kinds, 
both of the same length and thickness, but one kind 
with a head larger than that of the other. 

The large-headed pins are only placed in the centre 
of the square, the small-headed pins only on the 
sides, except in the single case of zero. Zero is 
marked by a large-headed pin placed in the centre 
of the small square which has no pin set on the sides. 
The figure i is represented by a small-headed pin, 
placed in the centre of the square, which has no pin 
set on its sides. The figure 2, by a large-headed pin 
placed in the centre of the square, and by a small- 
headed pin placed in one of the sides at the point 
I. The figure 3, by a large-headed pin placed in 
the centre of the square, and by a small-headed pin 
placed in one of its sides at the point 2. The figure 

4, by a large-headed \m\ placed in the centre of the 
square, and by a small-headed pin placed in one of 
the sides at the point 3. The figure 5, by a large- 
headed pin placed in the centre of the square, and by 
a small-headed pin placed in one of the sides at the 
point 4. The figure 6, by a large-headed pin placed 
in the centre of the square, and Vjy a small-headed pin 
placed in one of its sides at the j)oint 5. The figure 
7, by a large-headed pin placed in the centre of the 
square, and by a small-headed \)'\r\ placed in one of 
the sides at the point 6. The figure 8, by a large- 



92 DIDEROT S PHILOSOPHICAL WORKS 

• 

headed pin placed in the centre of the square, and 
by a small-headed pin placed in one of the sides 
at the point 7. The figure 9, by a large-headed 



ffl 



— (►-■ 



a 



79 — -^,- 



)r — % — ^1 



-(> Fig. 2. 



Fig. 3. 



pin placed in the centre of the square, and by a 
small-headed pin placed in one of the sides at 
the point 8. 

This gives ten different symbols for the sense of 
touch, each of which corresponds to one of our ten 



THE LETTER ON THE BLIND 93 

arithmetical characters. Now imagine a board as 
large as you choose, divided into small squares 
arranged horizontally and separated by a small 
space one from the other, as you see in fig. 4, and 
you have Saunderson's instrument. 

You can easily seie 'tlTat there is no number 
which cannot be expressed in the tablet, and 
hence no arithmetical process which cannot be 
carried out therein. 

Suppose, for example, that we want to find the 
sum of, or to add, the nine following numbers : — 



I 


2 


^ 



4 


5 


2 


3 


4 


5 


6 


3 


4 


5 


6 


7 


4 


5 


6 


7 


8 


5 


6 


7 


8 


9 


6 


7 


8 


9 





7 


8 


9 





I 


8 


9 





I 


2 


9 





I 


2 


J 



1 write them on the table in the order they are 
named : the first figure on the left of the first 
number, on the first square to the left of the first 
line ; the second figure on the left of the first 
number, on the second square on the left of the 
same line, and so on. 

I place the second number in the second row of 
squares ; units are units, tens are tens, etc. 

I place the third number in the third row of squares. 



94 DIDEROT'S PHILOSOPHICAL WORKS 

and so on, as you see in fig. 4. Next, touching 
with my fingers each vertical row from the top to 
the bottom, beginning with that which is most to 




iflj-fiif N-Jj* 



En 



u 



Fig. 4. 

my left, I add together the numbers therein ex- 
pressed ; and I write the tens that are over at the 
end of that column. I pass to the second column, 
moving leftward, and work in this way ; thence to 
the third, and so on completing my addition. 



THE LETTER ON THE BLIND 



95 



This is how the same tablet served him to prove 
the properties of rectilinear figures. Supposing he 
had to prove that parallelograms which have the 




mmwix 



Fig. 5. 

same base and same height are equal in area, he 
placed his pins as you see in fig. 5 ; he added names 
to the angles, and proceeded with the proof with 
his fingers. 

Supposing that Saunderson onl}- used large- 



96 DIDEROT'S PHILOSOPHICAL WORKS 

headed pins to mark the limits of his fingers, he 
could arrange round these small-headed pins of 
nine different varieties with all of which he was 
familiar. Thus he was never at a loss, except in 
cases where the great number of angular points 
which he was obliged to name in his proof forced 
him to have recourse to the letters of the alphabetT^ 
We are not told how he used them. 

We only know that his fingers moved over his 
tablet with astonishing rapidity ; that he made the 
longest calculations successfully ; that he could 
interrupt them, and recognise when he was in 
error ; that he could verify them with ease ; and 
that this work did not take him as much time as 
one might imagine, because he could arrange his 
tablet to suit his convenience. 

This arrangement consisted in placing large- 
headed pins in the centre of all the squares. This 
done, he had only to fix their value by small-headed 
pins, except in the case when he wished to express 
an unit. In that case he put a small-headed pin 
in the centre of the square, in place of the large- 
headed pin. 

Sometimes, instead of forming a complete line 
with pins, he only placed them at all the angles or 
points of intersection, and round these he stretched 
silk threads which completed his figures. (See 
fig. 6.) 

He left several other instruments which facilitated 
his geometrical studies ; the use he made of these 
is not known, and more acumen would perhaps be 




ICHOLA.S 

Lurafian R-ofeiror A 



//,//// 



O /<'/ nj. /// //.;-/ 



y 




of M a t hcinaiicks in . \ 



vy///./^ - 



/■Viit^V^wivA yt,t 






O'f^mtrCuJtf S.f/f 



To face p. 96. 



THE LETTER ON THE BLIND 



97 



required to discover this than to solve some problem 
in integral calculus. Let some geometrician try to 
discover the function of four pieces of solid wood 




Fig. 6. 

in the form of rectangular parallelepipeds, each 1 1 
inches by 5| wide and a little more than half an 
inch thick, and whose two larger opposite surfaces 
were divided into small squares similar to the 
abacus 1 have just described ; but with this differ- 

7 



98 DIDEROT S PHILOSOPHICAL WORKS 

ence, that they were only perforated at certain 
points, in which pins were driven in up to their 
head. Each surface had nine small arithmetical 




Fig. 7. 

tablets, each with ten numbers, and each of these 
ten numbers was composed of ten figures. Fig. 7 
represents one of the small tablets, and here are 
the numbers it contained : — 



THE LETTER ON THE BLIND 99 

94084 
24186 
41792 
54284 
63968 
71880 
78568 
84358 
89464 
94030 

He was the author of an excellent work of its 
kind — The Elements of Algebra}- — where the only 
signs of his blindness are the peculiarity of certain 
demonstrations which a sighted man would probably 
not have thought of. To him we owe the division 
of th e cube into six equal pyramids whose apex is 
at the centre of the cube and the base of each is 
one c{ its faces. This is used by him as a simple 
proof that every pyramid is the third of a prism 
having the same height and the same base. His 
taste for mathematics, his small means, and the 
advice of his friends decided him to give public 
leqtures. His marvellous facility for clear demon- 
stration encouraged his friends to think he would 
prove a successful teacher, for he taught his pupils 
as jf they could not see, and a blind man who makes 

' Printed in London, a year after Saunderson's death, at the expense 
of Cambridge University, In 1756 de Joncourt translated it, with some 
additional remarks (Amsterdam, 2 vols.). — (Hr) 



loo DIDEROT S PHILOSOPHICAL WORKS 

himself clear to the blind must be doubly lucid to 
the sighted ; it is a telescope the more. 

His biographers say that his talk ahoiiaded in 
N^happy expressions, and I can well believe it. But 
"What do you mean by happy expressions ? " you 
will perhaps inquire. I answer, madam, it is using 
expressions to one sense (touch, for example) 
which are also metaphorical to another sense (say, 
sight) : as a result, a double light is shed on the 
subject for the hearer, the direct light of the natural 
use of the expression and the reflected light of the 
metaphor. It is evident that in these cases, 
Saunderson, with all his intelligence, was not 
aware of the full force of the terms he employed, 
since he only realised half of the ideas attached to 
these terms. But does not this happen to all of 
us at times? It may happen to idiots, who some- 
times make excellent jokes, and clever folk who say 
a foolish thing, without either being aware of it. I 
have observed the want of words produces the like 
effect in foreigners, who in an unfamiliar language 
are obliged to say ever}thing in very few words, 
some of which they unknowingly use very happily. 
But every language being to writers of a lively 
imagination deficient in fit words, they are in the 
same case as clever foreigners : the situations 
invented by them, the delicate gradations they 
perceive in characters, the natural scenes they draw, 
are continually leading them away from ordinary 
locutions and causing them to adopt turns of phrases 
which never fail to charm when they are neither 



THE LETTER ON THE BLIND loi 

precious nor obscure. These are faults which are 
more or less readily forgiven, according to the 
reader's wit and knowledge of the language. This 

is why M. de M ^ is the French author who 

most pleases the English, and Tacitus, of all the 
classics, bears the bell among the thinkers ; they 
do not attend to the licences of the style, it is only 
the truth of the expression which strikes them. 

Saunderson was extremel)' successful as professor 
of mathematics at the University of Cambridge. 

"Hegamiessoiis in optics, he lectured on the nature 
of light and colours, he explained the theory of 
vision ; he wrote on the properties of lenses, the 

~plienomena of the rainbow, and many other subjects 
connected with sight and its organ. 

These facts lose much of their marvellous character 
when you consider that there are three distinct 
elements in a question in which both physics and 
geometry enter — the phenomenon to be explained, 
the hypotheses of the geometrician, and the resultant 
calculation. Now it is manifest that, however great 
the penetration of the blind man, the phenomena of 
light and colour are unknown to him. The hypotheses 
he will understand, as all of them relate to palpable 
causes ; but the geometrician's reason for preferring 
them to others will be out of his ken, as in order to 
see that he must be able to compare the hypotheses 

^ Naigeon, and afier him the editor of iSi8. have inserted, instead of 
the initials M. de M . . . in the original edition, M. de Montesquieu. 
This is a great mistake ; Diderot himself has given M. de Marivaux in 
the index of the 1749 and 1 75 1 editions. The Esprit des Lois appeared 
in 1748, which might have caused this error on the part of the editors, 
who had not consulted the index. — (Br) 



I02 DIDEROT'S PHILOSOPHICAL WORKS . 

themselves with the phenomena. Therefore the 
bhnd man takes the hypotheses for what they are 
given him, a ray of hght for a fine and elastic 
thread, or for a succession of minute bodies striking 
our eyes with incredible velocity, and he makes his 
calculations accordingly. The transition is made 
from physics to geometry, and the question becomes 
purely mathematical. 

But what are we to think of the results of the 
calculation ? Firstly, that it is sometimes extremely 
difficult to obtain them, and that it would be to little 
purpose that a man of science could form the most 
plausible h}'potheses, were he not able to verify 
them by geometry ; accordingly the greatest 
physicists, Galileo, Descartes, and Newton, were 
great geometricians. Secondly, the results are 
more or less certain, as the preliminary hypotheses 
are more or less complex. When the calculation is 
based on a simple hypothesis, the conclusions have 
the validity of geometrical proofs. When there are 
a great many suppositions, the probability of each 
hypothesis being true diminishes in the ratio of the 
number of these hypotheses ; but on the other hand 
increases owing to the improbability that so many 
false hypotheses could be mutually corrective and 
produce a result confirmed by the phenomena. A 
parallel to this would be an addition, of which the 
sum was correct although the sum of groups of 
numbers had been wrongly added up. We must 
admit that such a result is possible, but at the same 
time you see that it would very seldom prove so. 



THE LETTER ON THE BLIND 103 

The greater the number of numbers to be added, the 
greater the probability of error in the addition of 
each, but at the same time this probabiHty is 
lessened if the result of the operation be right. 
There are therefore a number of hypotheses, the 
certainty resulting from which would be the least- 
possible. If I make A plus B plus C equal to 50, 
must I conclude from 50 being the real quantity of 
the phenomena that the suppositions represented by 
the letters A, B, C are true ? Not at all, for there 
are numberless ways of subtracting from one of 
fliese^Ftefs and adding to the others which would 
always give 50 as the result. But the case of three 
combined hypotheses is perhaps one of the most 
disfavourable. 

One advantage of calculation which I must not 
omit is, that the contrariety found between the re- 
sult and the phenomenon excludes false hypotheses. 
If a man of science proposes to find the curve 
formed by a ray of light in passing through the 
atmosphere, he must regulate himself by the 
density of the strata of air, the law of refraction, 
the nature and form of the luminous corpuscles, and 
perhaps other essential factors which he does not 
include in his calculation, either because he does 
not know them or because he deliberately leaves 
them out of consideration. He then determines the 
curvature of the ray. If the actual curve differs 
from that of his calculation, his hypotheses are 
incomplete or false. If the actual curvature agrees 
with that of his calculation, there are two alterna- 



I04 D IDE ROT'S PHILOSOPHICAL WORKS 

tives : first that his hypotheses were mutually cor- 
rective, secondly that the}- were correct. But which 
is true ? He does not know, and yet that is the 
certitude to which he can attain. 

I read Saunderson's Elements of Algebra carefully 
in hopes of meeting what I was desirous of knowing 
from those who knew him intimately, and who have 
related some particulars of his life ; but my curiosity 
was baffled, and it occurred to me that elements of 
geometry from him would have been a work both 
more singular in itself and of greater use to us. We 
should have found in it definitions of point, line, 
surface, solid, angle, intersections of lines, and 
planes, in which I make no question but he would 
I have proceeded on principles of very abstract meta- 
physics, closely allied to that of the idealists. 
Those philosophers, madam, are termed idealists 
who, conscious only of their own existence and of a 
succession of external sensations, do not admit any- 
thing else ; an extravagant system which should to 
my thinking have been the offspring of blindness 
itself ; and yet, to the disgrace of the human mind 
and philosophy, it is the most difficult to combat, 
though the most absurd. It is set forth with equal 
candour and lucidity by Doctor Berkeley, Bishop of 
Cloyne, in three dialogues.^ It were to be wished 
that the author of the Essay on the Origin of Hjiinan 
Knoivledge - would take this work into examination ; 

^ Dialogties behueen Hylas and Philonoiis (1713), translated by the 
Abbe Gua de Malvin (1750). — (A) 

- Condillac (171 5-1780). whose Essay on the Origin of Human 
Knowledge had appeared anonymously in 1746. — (A) 



THE LETTER ON THE BLIND 105 

he would there find matter for useful, agreeable, 
and ingenious observation — for which, in a word, no 
person has a better talent. Idealism deserves an 
attack from his hand, and this hypothesis is a double 
incentive to him from its singularity, and much 
more from the difficulty of refuting it in accordance 
with his principles, which are the same as those of 
Berkeley. According to both, and according to 
reason, the terms essence, matter, substance, agent, 
etc., of themselves convey very little light to the 
mind. Moreover, as the author of the Essay on the 
Origin of Human Knowledge judiciously observes, 
whether we go up to the heavens, or down to the 
deeps, we never get beyond ourselves, and it is 
only our own thoughts that we perceive. And this 
is the conclusion of Berkeley's first dialogue, and the 
foundation of his entire system. Would you not 
be curious to see a trial of strength between two 
enemies whose weapons are so much alike? If 
either got the better it would be he who wielded 
these weapons with the greater address ; the author 
of the Essay on the Origin of Human Knowledge has 
lately given in his Treatise on Systems additional 
proof of his adroitness and skill and shown himself a 
redoubtable foe to the systematics. 

We have wandered far from the blind, you will 
say. True, madam, but you must be so good as to 
allow me all these digressions ; I promised you a 
conversation, and I cannot keep my word without 
this indulgence. 

I have read as carefully as it was in my power 



io6 DIDEROT S PHILOSOPHICAL WORKS 

what Saunderson has said on the infinite ; and I 
assure you he had such very just and very clear 
notions on the subject that in his account most of 
our infinitarians would have been looked on but as 
blind. You yourself shall be judge : though this 
matter be somewhat difficult, and a little beyond 
your mathematical knowledge, I trust to bring it 
witliin your grasp and initiate you into the logic of 
the infinite. 

The case of this famous blind man proves that the 
sense of touch, when trained, can become more 
delicate than sight, for he distinguished genuine 
from counterfeit coins ^ b}- passing his hands over 
a number of these, although the counterfeits were 
, sufficiently good imitations to deceive a clear- 
sighted connoisseur ; and he judged of the accuracy 
of a mathematical instrument by passing the tips 
of his fingers along its divisions. This is certainly 
more difficult than to judge by touch of the resem- 
blance of a bust to the person represented, and this 
shows that a blind people might have sculptors and 
put statues to the same use as among us to per- 
petuate the memory of great deeds, and of persons 
dear to them ; and in my opinion feeling such 
statues would give them a keener pleasure than we 
have in seeing them. What a delight to a passion- 
■" ate lover to draw his hand over beauties, which he 
would know again, when illusion, which wauld act 
more potently on the blind than on those who see, 

^ Memoirs of the life and character of Dr Nicholas Saunderson in 
Saunderson's Algebra, vol. i, p. xi (1740). 



THE LETTER ON THE BLIND 107 

should come to reanimate them ! But perhaps, as 
hu^U'ouTdTake a deeper pleasure in the memory, his 
grief would be the keener for the loss of the original. 

SajLmderson, like the blind man of Puisaux, was 
affected by the smallest atmospheric change, and 
could recognise, especially in still weather, the 
presence of objects not far from him. It is related 
of him that being present during some astronomical 
observations taken in a garden, the cjouds which 
hid tlie face of the sun every now and then from 
the spectators at the same time caused such a change 
in the action of the rays on his face as signified 
to him the moments which favoured or impeded 
the experiments. You may, perhaps, think that 
some change in the eye might indicate to him the 
presence of light, but not of distant objects, and I 
would have supposed so myself, but for the fact 
that Saunderson had lost not only his sight but 
its organ. 

Saunderson, then, saw by means of his skin, and 
this integument of his was so keenly sensitive that 
with a little practice he could certainly have re- 
cognised the features of a friend traced upon his 
hand, and would have exclaimed, as the result of 
successive sensations caused by the pencil: " Tliat 
is sq-and-sc" Thus the blind have likewise a j^iaint- 
ing, in which their own skin serves as the canvas. 
'These are no wild fancies, and I am sure if the little 

mouth of M were traced on your hand, you would 

immediately recognise it. Yet you must allow the 
blind man would find this an easier task than you, 



1 



io8 DIDEROT'S PHILOSOPHICAL WORKS 

accustomed though you are to see and admire that 
mouth. For two or three elements enter into your 
recognition : the comparison of the tracery on your 
hand with the picture formed on the ground of your 
eye ; the recollection of the manner in which we are 
affected by things felt, and of the manner with which 
we are affected by things we have only seen and 
admired ; finally, the application of these data to the 
question of the draughtsman, who asks you when 
he draws with his pencil a mouth on the skin of your 
hand : " Whose mouth is this which I am drawing ?" 
Whereas the sum of the sensations aroused by a 
mouth laid on the blind man's hand is the same as 
the sum of the successive sensations caused by the 
draughtsman's pencil. 

I might add to this account of Saunderson and 
the blind man of Puisaux, Didymus of Alexandria, 
Eusebius the Asiatic, and Nicaise of Mechlin,^ and 
some other people who, though lacking one sense, 
seemed so far above the level of the rest of mankind 
that the poets might without exaggeration have 
feigned the jealous gods to have deprived them of it, 
from fear lest mortals should equal them. For what 
was Tiresias, who had penetrated the secrets of the 
gods, but a blind philosopher whose memory has 
been handed down to us by fable ? But let us 
return to Saunderson and follow the history of this 
extraordinary man to his grave. 

When he was at the point of death, ^ a clergyman 
of great ability, Mr Gervase Holmes, was summoned 

^ See note 2, pp. 219, 220. " See Introduction, pp. 10-15, ^^j ^Q- 



THE LETTER ON THE BLIND 109 

y 

to his side, and they held a discussion upon the \^ 
existence of God, some fragments of which are 

exfant, and which I will translate to the best of my . 

ability, for they are well worth it. The clergyman ~^ 
began by haranguing on the wonders of nature. I 
"Ah, sir," replied the blind philosopher, "don't 
talk to me of this magnificent spectacle, which it has 
never been my lot to enjoy. I have been condemned 
to spend my life in darkness, and you cite wonders 
quite out of my understanding, and which are only 
evidence for you and for those who see as you do. 
Ifyou want to make me believe in God you musfr^f 
make me touch Him." "Sir," returned the clergy-~^ 
man, very appositely, "touch yourself, and you 
will recognise the Deity in the admirable mechanism 
oT^your organs." 

"Mr Holmes," replied Saunderson, "I must 
repeat it, all that does not appear so admirable to 
rne[as to you. But even if the animal mechanism 
were as perfect as you maintain, and I dare say it is 
(for you are a worthy man and would scorn to 
impose on me), what relation is there between such 
(ffiechanism and a supremely intelligent Being? If 
it^fills you with astonishment, that is perhaps 
because you are accustomed to treat as miraculous 
everything which strikes you as beyond your own 
powers. I have been myself so often an object of 
admiration to you, that I have not a very high 
idea of your idea of the miraculous. I have had 
visits from people from all parts of England who 
could not conceive how I could work at geometry : 



no DIDEROT S PHILOSOPHICAL WORKS 

you must allow such folk not to have been very 
exact in their notions of the possibility of things. 
We think a certain phenomenon beyond human 
power and we cry out at once : ' 'Tis the handiwork 
of a god ' ; our vanity will stick at nothing less. 
Why can we not season our talk with a little less 
pride and a little more philosophy ? If nature offers 
us a knotty problem, let us leave it for what it is, 
without calling in to cut it the hand of a being who 
immediately becomes a fresh knot and harder to 
untie than the first. Ask an Indian how the earth 
hangs suspended in mid-air, and Tie will tell you 
that it is carried on the back of an elephant ; and 
what carries the elephant ? A tortoise. And the 
tortoise? Vou pity the Indian, and one might 
say to yourself as to him : ' My good friend Mr 
Holmes, confess your ignorance, and drop the 
elephant and the tortoise.'"^ 

Saunderson paused, apparently waiting for a 
reply, but what possible reply was there to the 
blind man ? Mr Holmes availed himself of his good 
opinion of his probity and of the abilities of Newton, 
Leibniz, Clarke, and some of his fellow-countrymen, 
men of the highest genius, who had all been im- 
pressed by the wonders of nature and recognised an 
intelligent being as its creator. This was certainly 
the clergyman's strongest argument. The blind man 
admitted that it would be presumptuous to deny 
what such a man as Newton had acquiesced in ; yet 
he represented to the clergyman that Newton's 

^ See note 3, pp. 221, 222. 



THE LETTER ON THE BLIND in 

evidence was not of that weight to him, as that ^ ~ 
of a ll nature to Newton ; while Newton believed 
on G od's word, he was reduced to believe on 
Newton's word. 

"Consider, Mr Holmes," he added, "what a 
confidence I must have in your word and in 
Newton's. Though I see nothing, I admit there is 
in everything an admirable design and order. I hope 
you will not demand more. I take your word for 
the present state of the universe, and in return keep 
the liberty of thinking as I please on its ancient and 
primitive state, with relation to which you are as 
blind as myself. Here you will have no witnesses 
to confront me with, and your eyes are quite use- 
less. Think, if you choose, that the design which 
strikes you so powerfully has always subsisted, but 
allow me my own contrary opinion, and allow me 
to believe that if we went back to the origin of-^^ 
things and scenes and perceived matter in motion 
and thejevolution from chaos, we should meet with 
a number of shapeless creatures, instead of a few 
creatures highly organised. 1 make no criticism o\\\ 
the present state of things, but I can ask you some 
questions as to the past. For instance, I may ask 
you and Leibniz and Clarke and Newton, who told *^ 
you that in the first instances of the formation of i 
animals some were not headless and others footless ? ; 
I might affirm that such an one had no stomach, j 
another no intestines, that some which seemed to 1 
deserve a long duration from their possession of a , 
stomach, palate, and teeth came to an end owing 



112 DIDEROT'S PHILOSOPHICAL VVOPKS 

to some defect in the heart or lungs ; that monsters 
mutually destroyed one another ; that all the 
defective combinations of matter disappeared, and 
that those only survived whose mechanism was not 
defective in any important particular and who were 
able to sujjport and perpetuate themselves,^ 

" Suppose the first man had his larynx closed, or 
had lacked suitable food, or had been defective in 
the organs ot generation, or had failed to find a 
mate, or had propagated in another species, what 
then, Mr Holmes, would have been the fate of the 
human race? It would have been still merged in 
the general depuration of the universe, and that 
proud being who calls himself man, dissolved and 
dispersed among the molecules of matter, would 
have remained perhaps for ever hidden among the 
number of mere possibilities. If shapeless creatures 
had never existed, you would not fail to assert that 
none will ever appear, and that I am throwing 
myself headlong into chimerical fancies, but the 
order is not even now so perfect as to exclude the 
occasional appearance of monstrosities." Then, 
turning towards the clergyman, he added, "Look 
at me, Mr Holmes. I have no eyes. What have 
we done, you and I, to God, that one of us has 
this organ while the other has not ? " 

Saunderson uttered these words in such a sincere 
and heartfelt tone that the clergyman and the rest 
of the company could not remain insensible to his 

^ This is the thesis of Lucretius, and the theory of the survival of the 
fittest.— (A) 



THE LETTER ON THE BLIND 113 

suffering, and began to weep bitterly. He noticed 
~~Tr^nd said to the clergyman, "Mr Holmes, I was 
aware of the kindness of your heart, and I am very 
grateful for the expression of it you have given 
me just now ; but if you love me, do not grudge 
me my dying consolation of never having caused 
anyone affliction." 

Then, continuing the conversation in a firmer 
tone, he added: "I conjecture, then, that in the 
beginning, when matter in a state of ferment 
brought this world into being, creatures like myself 
were of very common occurrence. But might not 
\^rlds too be in the same case ? How many faulty -^ 
and incomplete worlds have been dispersed and 
perhaps form again, and are dispersed at every 
instant in remote regions of space which I cannot 
touch nor you behold, but where motion continues 
and will continue to combine masses of matter, 
jintil they have found some arrangement in which 
they may finally persevere ? O philosophers, travel 
with me to the confines of this universe, beyond the 
point where 1 feel and you behold organised beings ;v 
cast your eyes over this new ocean, and search in its 
aimless and lawless agitations for vestiges of that 
intelligent Being whose wisdom fills you with such 
wonder and admiration here ! 

"But what is the use of taking you out of your 
element ? What is this world, Mr Holmes, but a 
complex, subject to cycles of change, all of which 
show a continual tendency to destruction ; a rapid 
succession of beings that appear one by one, flourish 



114 DIDEROT S PHILOSOPHICAL WORKS 

and disappear ; a merely transitory symmetry and 
momentary appearance of order ? A moment ago 
I reproached you for estimating the perfection of 
things by your own capacity ; I might accuse you 
here of measuring duration by your own existence. 
You judge of the phases of the world's existence as 
the ephemeral insect of yours. The world seems to 
you eternal, just as you seem eternal to the creatures 
of a day ; and the insect is more reasonable than 
you. What a prodigious series of ephemeral genera- 
tions witness to your eternity, what an immense 
tradition ! Yet we shall all pass away without a 
possibility of denoting the real extent which__we 
took up, or the precise time of our duration. Time, 
matter, and space are perhaps but a point." 

During this conversation Saunderson became 
more excited than his state of health would permit, 
and an attack of delirium ensued, which lasted 
several hours. At its close he cried, " O thou God 
of Clarke and Newton, have mercy on me I" and 
expired. 

Such was the end of Saunderson. You see, 

r madam, that all the arguments of the clergyman he 

I took exception to were not of a character to con- 

i vince a blind man. \AVhat a disgrace to men who 

- / have no better argument than he ; men who have 

^ / eyes, to whom the marvellous spectacle of nature 

I from sunrise to the setting of the smallest stars 

^^l ^reveals the existence and glory of its Maker ! They 

have sight, which Saunderson was deprived of, but 
Saunderson was blessed with a purity of life and 



THE LETTER ON THE BLIND 115 

uprightness which we look for in vain in them, v 
Accordingly they lead the life of the blind, and 
SaunSTerson died as if he knew the light. The voice 
^of^nature made itself clear to him by the media of 
the senses he possessed, and his evidence is the 
more convincing against those who obstinately shut / 
their eyes and ears. Was not the true God more 
completely veiled by the mists of paganism for a 
Socrates, than for the blind Saunderson, who never 
enjo}-ed the spectacle of nature ? 

I am very sorry, madam, both for your sake and 
mine, that no further interesting particulars of this 
famous blind man have been handed down. His 
conversation would perhaps have afforded more light 
than all our experiments. Those about him must i 
have been devoid of the philosophic spirit. I make an 
exception in favour of his pupil, Mr William Inchlif, 
who only saw Saunderson during his last moments, 
and who took down his last words, which I should 
advise all who know English to read irt the original, 
printed in Dublin in 1747, and entitled The Life and 
Character of Dr Nicholas Saunderson, late Lucasian 
Professor of the MatJiematicks in the University of 
Cambridge; by his disciple and friend William 
Inchlif, Esq.^ They will find a charm, and a 
vigour in this, scarce ever paralleled, but which I y 
do not flatter myself I have conveyed in translation, 
in spite of all my care. 

' By rentlering a Dr Inchlif responsible fur his imaginary reconstruc- 
tion of Saundcrson's last moments Diderot alienated the sympathies of 
England. — (A) 



ii6 DIDEROT'S PHILOSOPHICAL WORKS 

He married in 171 3 the daughter of Mr Dickons, 
rector of Boxworth, in the county of Cambridge, and 
had by her a son and daughter who are still living. 
His farewell to his family was exceedingly moving. 
"I go," said he, "to our common destination; 
spare me laments which unman and unnerve. The 
expressions of grief which escape you only make 
me conscious of my own. I gladly give up a life 
which has been for me a long desire, a constant 
privation. Live on, as virtuous as I, but more 
fortunate, and learn to die with equal calm." He 
then took his wife's hand, which he held for a moment 
clasped in his own ; he turned his face towards her as 
if he desired to see her ; he blessed his children, 
embraced them, and begged them to leave him, 
because they caused him greater grief than the 
approach of death. 

England is the land of philosophy and of scientific 
inquiry, yet without Mr Inchlif we should only 
know what the common man could have narrated of 
Saunderson ; for instance, that he recognised places 
he had once visited by the sound the walls and 
pavement reflected, and man}' similar anecdotes, 
all equally common to the majority of the blind. 
Strange ! Arc blind men of such high intellectual 
abilities as Saunderson of common occurrence in 
England, and are men born blind who lecture on 
optics to be met with every da}' ? 

People try to give those born blind the gift of 
sight, but, rightly considered, science would be 
equally advanced by questioning a sensible blind 



THE LETTER ON THE BLIND 117 

man. We should learn to understand his psycholog)- 
and should compare it with ours, and perhaps we 
should thereby come to a solution of the difficulties 
which make the theory of vision and of the senses 
so intricate and so confused. But I own I cannot 
conceive what information we could expect from a 
man who had just undergone a painful operation 
upon a very delicate organ which is deranged by the 
smallest accident and which when sound is a very "^ 
untrustworthy guide to those who have for a long / 
time enjoyed its use. For my part, as to the theory' 
of the senses, 1 would sooner hear a metaphysician 
who was acquainted with the principles of meta- 
physics, the elements of mathematics, and the con- 
formation of the organs of sense, than an uneducated 
man whose sight was first due to an operation for 
cataract. I would have less confidence in the im- 
pressions of a person seeing for the first time than 
in the discoveries of a philosopher who had profoundly 
meditated on the subject in the dark ; or, to adopt 
the language of the poets, who had put out his eyes 
in order to be the better acquainted with vision. 

To obtain some certainty in such experiments the 
subject must at least have been prepared a long time 
beforehand ; he should be made a philosopher — no 
rapid process even with a philosopher for teacher ! 
And imagine the task if the teacher were not 
enlightened, or (worse still) fondly and mistakenly 
imagined himself enlightened ! It would be better 
to postpone the investigation to a considerable period 
after the operation. To do this, the patient would 



ii8 DIDEROT S PHILOSOPHICAL WORKS 

have to remain in darkness, and the investigator 
would have to see to it that his wound was healed 
and his eyes perfectly sound. I would not expose 
him to full daylight for the first time. A strong 
light dazzles our eyes ; what effect will it not have 
on an organ which cannot but be extremely tender 
and sensitive, and which has never yet felt any 
impression to blunt it ? 

But this is only the beginning. It would be a 
difficult and deHcate task to reap any benefit even 
from a person thus prepared, and to adapt our 
questions so that he may precisely say only what 
passes in himself. This interrogatory should be 
held in presence of the Academy ; or rather, to avoid 
the presence of idle spectators, only such as deserve 
that distinction by their knowledge of philosophy, 
anatomy, etc., should be invited. 

The task would not be beneath the intelligence of 
the best and wisest of men ; to train and question 
one born blind would be an occupation worthy of 
the combined talents of Newton, Descartes, Locke 
and Leibniz, 

I will end my letter, which I own is already too 
lengthy, by a problem which was propounded some 
time ago. Some reflections upon Saunderson's 
singular condition tend to show that it has never 
been absolutely solved. Suppose one blind from 
birth has been taught to distinguish by touch a cube 
and a sphere of the same metal and of approximately 
the same size, so that when he touches them he can 
say which is the cube and which is the sphere. 



THE LETTER ON THE BLIND 119 

Suppose the cube and sphere placed on a table 
and the blind man suddenly to see ; can he dis- 
tinguish the cube from the sphere by sight without 
touch ? "Ncf^' 

KTr Molyneux first stated this problem and / 
attempted to solve it. He declared that the blind \ 
man would not distinguish between the cube and 
tHe'sphere ; "for," said he, "though he has learnt 
by experience the effect of a sphere and a cube upon 
the sense of touch, he does not yet know that what 
affects his sense of touch in such and such a manner 
must affect his sight thus or thus ; nor that the pro- 
jecting angle of the cube which presses against his 
hand should appear to his eyes as it actually does 
appear in the cube." 

Locke, 1 when consulted on this point, said : "I 
certainly agree with Mr Molyneux's opinion. I 
believe the blind man incapable at first sight of 
affirming with any certainty which was the cube 
and which the sphere if he merely looked at them, 
although, if he touched them, he could name them 
and distinguish between them by the difference of 
their shape, which he would recognise by touch." 

The Abbe de Condillac,^ whose Essay on the Origin ^ 
o f Hum an Knowledge you have read with so much 
pleasure and profit, and whose excellent Treatise on 
Systems accompanies this letter, makes an original 
contribution to the question. I shall not repeat his 
arguments here, since you will have the pleasure of 
reading his book in which they are expounded in 
' See note 4, pp. 222, 223. "^ See note 5, pp. 223-5, 



I20 DIDEROT S PHILOSOPHICAL WORKS 

■ such an entertaining and yet such a philosophical 
manner that it would be a mistake on my part to 
tear them from their context. I shall merely observe 
—^that they all tend^to prove that the born-blind either 
\ sees nothing, or distinguishes between the sphere 
' and the cube ; and that the conditions that these 
two bodies should be of the same metal and of 
approximately the same size (which was postulated 
in the problem) are unnecessary, which cannot be 
disputed ; for he might have said, if there be no 
essential connection between the sensations of the 
sight and the touch (as Messrs Locke and Molyneux 
assert), they must admit that a body may to the eye 
appear to have two feet in diameter which yet would 
vanish on being touched. De Condillac adds, how- 
ever, that if the blind man sees bodies and dis- 
tinguishes their forms, and yet hesitates what to 
think about them, it must be from metaphysical 
reasons, and those not a little subtle, which I shall 
presently explain. We have here two different 
opinions on the same question — a difference between 
philosophers of the highest rank. One would 
suppose, after the problem had been studied by 
men such as Messrs Molyneux, Locke and the 
Abbe de Condillac, that nothing more could be 
said ; but the same thing can be viewed from so 
many different sides that it is not strange if they 
have not exhausted all its possibilities. 

Those who declare that a mari blind from birth 
could not distinguish between a cube and a sphere 
have set out by assuming a fact which perhaps should 



THE LETTER ON THE BLIND 121 

have been investigated ; that is, whether a bhnd man 
who has had his cataracts removed is^n a condition 
to use hjs_eyes immediately after the operation. 
They merely say : "The blind man, comparing the 
ideas of spheres and cubes which he has received by 
the sense of touch with those received by sight, will 
necessarily know them to be the same ; and it would 
be indeed odd if he were to name that body a cube 
which gives the eye the idea of a sphere, and sphere 
that which gives the idea of a cube. He will there- 
fore call those bodies spheres and cubes at sight 
which he called spheres and cubes by the sense of 
touch." 

But how do their antagonists reply ? The}' have 
also taken for granted that the Hind man could see 
immediately his organ was perfect ; they supposed 
that an eye couched for cataract was like an arm 
that ceases to be paralysed. As the latter does not 
need exercise before it feels, they said, neither does 
the former before it sees ; and they added : " Let 
us grant the blind man a little more philosophy 
than you afford him, and after carrying on the reason- 
ing where you left it, he will continue thus : ' But 
stillj who is to assure me that when I approach 
these bodies and touch them with my hands they 
win not on a sudden deceive my expectation, and 
that a cube will not give me the sensation of a sphere 
and a sphere of a cube ? Experience alone can teach 
me whether there be an analogy between sight and 
touch. The reports of these two senses may well 
be contradictory without my knowing it ; nay, 1 



-ni 



122 DIDEROT S PHILOSOPHICAL WORKS 

should perhaps suppose what is actually present to 
the sight to be only a mere appearance, had I not 
been informed that they are the very same_bodies 
I had touched. This object certainly seems to be 
the body which I called a cube ; and that, the body 
I called a sphere ; but the question is, not what 1 
think^ but what is ; and I am not in a position to 
answer the latter question satisfactorily,'" 

The line of argument, says the author of the 
Essay on the Origin of Human Knowledge, would be 
extremely perplexing to him who had been born 
blind, and I see nothing but experience which can 
furnish an answer to it. It seems probable that 
the Abbe de Condillac means only the experiment 
repeated by the blind man himself on a second 
handling of these bodies. You will soon perceive 
why I make this point. That able metaphysician 
might have added that the blind man would be 
the more inclined to suppose that two senses might 
be mutually contradictory, as he conceives that a 
mirror makes them mutually contradictory, as I 
have noticed already. 

De Condillac proceeds to observe that Molyneux 
has confused the issues of the problem by laying 
down several conditions which are irrelevant to the 
metaphysical difficulties which the blindjnan -would 
experience. This criticism is the more just, as the 
supposition of the blind man being acquainted with 
metaphysics is not at all out of the way; because the 
experiment in all such philosophical questions should 
be accounted to be made on a philosopher — that is 



THE LETTER ON THE BLIND 123 

to say, on a person who perceives in the questions 
propounded all that his reason and the state of his 
organs permit him to perceive. Such, briefly, 
are, madam, the pros and cons of the problem ; 
and you shall now see by my examination of it 
how very far they, who asserted that the blind 
man would see geometrical figures and distinguish 
between them, were from realising that they were 
right ; and what good reason their opponents had 
to think that they were not in the wrong. 

This problem of the blind man, stated in some- 
what more general terms than by Molyneux, / 
embraces two problems which we will consider 
separately. We may ask (i) if the blind man would 
see imme diately after the operation for cataract ; 
(2) supposing he is able to see, could he see well 
enough to distinguish between figures ; could he, 
in seeing^Kem, correctly give them the same names 
which he gave them by the sense of touch ; and if J 
he can, prove that these names are the right ones ? "^ 

Will the man born blind see immediately after 
the cure of the organ ? Those who maintain that 
he will not see, say: "Directly the blind man is 
able to use his eyes, all the scene before him is 
represented at the back of the eye. This image, 
which is composed of a number of objects concen- 
trated in a very small space, is but a confused mass 
of figures which he will not be able to distinguish 
People are on the whole agreed that it is only ex- 
perience which can enable him to judge of the dis 
tance of objects, and that he is obliged to approach, 



124 DIDEROT S PHILOSOPHICAL WORKS 

touch, draw back from, and again approach and 
touch them to assure himself that they are not part 
of himself and are foreign to his essence ; that he 
is now near and now far from them. Why should 
not experience be a necessary preliminary for per- 
ceiving them ? Without previous experience he who 
perceives objects for fehe first time would suppose, 
when he is out of sight of them, that they had 
ceased to exist ; for it is only our experience of per- 
manent objects and such as we find again in the 
same place where we left them which evidences 
the continuity of their existence when out of our 
sight. It is perhaps for this reason that children 
are so readily consoled for toys taken from them. 
It cannot be said that they promptly forget them, 
for some children only two and a half years old 
know a considerable number of words of a language 
and are more at a loss to pronounce them than to 
retain them. Now, this is a proof of childhood's 
being the very season of memory. 

Is it not a more likely hypothesis that children 
think that what they no longer see no longer exists, 
especially as their joy when things they have lost 
sight of appear again is mixed with surprise ? 
Nurses help them to acquire the notion of the 
continuance of absent persons by playing a game 
which consists in hiding the face, and showing it 
again. Thus they learn a hundred times in a 
quarter of an hour that what ceases to appear does 
not necessarily cease to exist. Whence it follows 
that we owe the notion of the continuous existence 



THE LETTER ON THE BLIND 125 

of objects to experience, of their distance to the 
sense of toucH ; that the eye may perhaps have to 
learn to see as the tongue to speak ; that it would 
not be surprising should the aid of one of the 
senses be necessary to another ; and that touch, 
which ascertains the existence of objects exterior to 
ourselves when present to our eyes, is likewise the 
sense to which the confirmation not only of their 
figures, and other details of these objects, but even 
their presence, is reserved. 

To these arguments may be added the famous 
experiment of Cheselden. ^ The young man from 
whose eyes this skilful surgeon removed cataracts 
was for a long time unable to distinguish dimensions, 
distances, positions, or even figures. An object an 
inch in size held before his eye so as to hide a house 
from him appeared as large as the house itself. All 
he saw seemed as close to his eye as the object 
he touched to the skin. He could not distinguish 
what he judged round by touch from what he had 
judged angular ; nor distinguish by sight whether 
what he had felt to be above or beneath him were 
in reality above or beneath him. He eventually 
succeeded, but not without difficulty, in perceiving 
fhat his house was larger than his room, but he 
could not conceive how this could be ascertained by 
sight. Repeated experiments were necessary before 
^e^^came assured of paintings representing solid 
bodies ; and when he was quite convinced by looking 
at pictures that what he saw was not bare surfaces, 

' See note 6, p. 225. 



126 DIDEROT S PHILOSOPHICAL WORKS 

on putting his hand to a picture he was vastly 
surprised at finding a plane surface without any 
relief. He then asked which was deceptive, the 
sense of touch or the sense of sight ? Painting 
likewise has the same effect on savages. They take 
the painted figures for living men, question them 
and are astonished at receiving no answer ; and 
this error in them certainly did not proceed from 
their not being accustomed to see. 

But what can be answered to the other difficulties ? 
That the trained and practised eye of a man sees 
better than the weak and untrained organ of an 
infant, or of one born blind who has had his eyes 
couched. Look, madam, at the proofs adduced 
by the Abbe de Condillac at the end of his Essay 
on the Origiii of Human Knowledge^ where he also 
adduces Cheselden's experiments as related by 
Voltaire. The effects of light upon an eye for the 
first time so affected, and the conditions required in 
humours of that organ, the cornea, the cr}stalline 
lens, etc., are clearly and ably specified therein, 
and leave little doubt that the vision of an infant 
opening its eyes for the first time, or a blind person 
who has just been operated upon, is very imperfect. 

We must, therefore, admit we perceive a multitude 
of details in objects unperceived by the infant or 
one born blind, though these objects are equally 
represented at the back of their eyes ; for objects 
to strike us is not enough — we must further attend 
to these experiences ; that, consequently, we see 
nothing the first time we use our eyes ; and during 



THE LETTER ON THE BLIND 127 

the first moments of sight we only receive a mass of 
confused sensations, which are only disentangled 
after a time and by a process of reflection. It is 
by experience alone that we learn to compare our 
sensations with what occasions them ; that sensa- 
tions having no essential resemblance with their 
objects, it is from experience that we are to inform 
ourselves concerning analogies which seem to be 
merely positive. In short, that touch is of great ' 
service in giving the eye an accurate knowledge of 
the conformity of the object to the sense-impression 
received of it is unquestionable ; and I am much 
inclined to think that were not everything in nature 
subject to laws infinitely general — if, for instance, 
the pricking of certain hard bodies were painful, 
and that of certain other bodies pleasurable — we 
should die before we had received the hundred- 
millionth fraction of the experiences necessary for 
the preservation of our body and our well-being. 

I am not, however, of opinion that^ the eye is 
incapable of learning, or, if I may say so, of ex- 
perimenting alone. To ascertain the existence and 
form of objects by touch, there is no necessity of 
seeing ; why should touch be necessary for complete 
realisation of the same objects by sight ? I am 
awake to all the advantages of touch ; I have not 
disguised them in these observations on Saunderson 
or the blind man of Puisaux ; but I cannot allow it 
that prerogative. It is easy to see that the use of 
one sense may be perfected and accelerated by the 
observations of another ; but not tHat there is an 



128 DIDEROT S PHILOSOPHICAL WORKS 

essential interdependence between their functions. 
There exist certainly properties in bodies which we 
should never perceive without touch ; and by touch 
we learn the presence of certain details invisible to 
the eye, which only becomes aware of these when 
informed by the sense of touch ; but their services 
are mutual ; and in the case of persons who have 
sight more highly developed than touch it is the 
former which warns the latter of the existence of 
objects and of details which would pass unnoticed 
from their minuteness. If unknown to you a piece 
of paper or some smooth, thin, and flexible substance 
were placed between your thumb and index finger, 
it is your eye alone which would inform you that 
the contact between your two fingers was not direct. 
It would be much more difficult, I may cursorily 
add, to deceive a blind man than a person used to 
see in this. 

An eye which is in sound condition and freely 
exercised might have some difficulty in convincing 
itself that exterior objects are not part of itself ; 
that some things are distant, some near ; that they 
have forms ; that some are larger than others ; that 
they have depth, etc. ; still, I make no doubt that 
at length it would come to see them, and to see 
them so distinctly as to distinguish at least their 
more obvious limits. 

To deny this would be to set aside the aim and 
object of the organs ; it would be forgetting the 
chief phenomena of vision ; it would be concealing 
from oneself that there is no painter of such skill 



THE LETTER ON THE BLIND 129 

as to rival the beauty and exactness of the miniatures 
which are painted in the back of your eyes ; that 
there is nothing more exact than the likeness of the 
representation to the object itself; that the canvas 
of this picture is not so very small, that there is 
no confusion among the various forms, and that they 
occupy about a square half-inch ; and that nothing 
is more difficult to explain than how the sense of 
touch would begin to teach the eye to see were the 
use of the latter organ absolutely impossible without 
the aid of the former. 

But, instead of bare presumptions, I ask you 
whether it is touch that teaches the eye to distinguish 
colours ? I do not suppose such an extraordinary 
claim will be made for touch ; and this being so, it 
follows that if a blind man who has just been given 
the gift of sight is shown a black cube or a red 
sphere on a white background, he will immediately 
discern the several outlines of these figures. 

Delay will be caused, some may object, by the 
time which must elapse for the humours of the eye 
to assume their proper dispositions, for the cornea 
to assume the convexity requisite for vision, for the 
pupil to be susceptible of the dilation and contraction 
I)roper to it, for the filaments of the retina to be 
sensitive in the right degree to the action of light, 
for the crystalline to exercise its forward and back- 
ward movement or for the muscles to fulfil their 
functions well, for the optic nerves to become 
accustomed to the transmission of sensation, for 
the entire eyeball to accommodate itself to all the 

9 



130 DIDEROrS PHILOSOPHICAL WORKS 

necessary dispositions, and for all its component 
parts to combine in the execution of that miniature, 
which so much illustrates the demonstration that 
the eye will bring itself to the requisite experience. 

I own that, plain as the picture is which I have 
now represented to the eye of one born blind, he 
will not be able clearly to distinguish its parts until 
all these above conditions are combined ; but that 
is perhaps the work of a moment ; and it would 
not be difficult, by applying the aforesaid argument 
to a complicated mechanism such as a watch, to 
prove by enumerating all the movements which 
take place in the drum, the fusee, the wheels, the 
pallets, the pendulum, etc., that the hand would 
take a fortnight in moving the space of a second. 
If it is objected that these movements are simulta- 
neous, I reply that so perhaps are the movements 
in the eye when it opens for the first time, and 
most of the consecutive judgments. Whatever are 
the conditions in the eye requisite for vision, it 
must be granted that it is not touch which imparts 
them to it, that the organ acquires them independ- 
ently ; consequently, will succeed in distinguishing 
the figures represented therein without the aid of 
another sense. 

But when does this occur ?, some will say. 
Perhaps far sooner than is thought. When we 
went together to the Jardin Royal, do you 
remember the experiment with the concave mirror 
and your fright when you saw the point of a sword 
making at you with the same swiftness as the point 



THE LETTER ON THE BLIND 131 

of that which you pushed towards the surface of the 
mirror? And yet you were sufficiently accustomed 
to refer objects represented in mirrors to something 
beyond them. Experience, therefore, is not so 
very necessary, nor so infalHble as imagined, for 
perceiving objects or their images where they are. 
Your very parrot gives proof of it. The first time 
he saw himself in a mirror, he touched it with his 
beak, and as he did not reach himself (whom he 
took for a fellow-parrot) he walked round the mirror. 
I am not for laying more than due weight on the 
instance of the parrot ; still, it is an experiment with 
an animal in which preconceived notions cannot be 
supposed to have any share. 

Yet if I were told that a man born blind saw 
nothing for the space of two months, I should not 
be surprised. I shall only conclude from it the 
necessity of the organs becoming practised, not the 
necessity of touch. It will be another reason why 
it is important to let such a person remain for some 
time in the dark, when he is to be the subject of 
experiment ; to allow him the opportunity of exer- 
cising his eye, which will be done more conveniently 
in the dark than in full daylight ; and only to 
pefmrr'a^^ind of twilight during the experiments, 
or at least to arrange for the increasing or diminish- 
ing of light at pleasure in the spot where the 
experiments take place. I shall only be the more 
inclined to agree that such experiments will always 
be very difficult and uncertain ; and that the best 
and shortest (though superficially the longest) way 



132 DIDEROrS PHILOSOPHICAL WORKS 

would be to arm the subject with a philosophical 
training sufficient to enable him to compare tTie two 
conditions he has known, and to acquaint us with 
the difference between the state of a blind person 
and of one who has his sight. Once more, what 
precision is to be expected from one who has ndt 
the habit of thought and analysis, and who, like 
Cheselden's blind man, is so ignorant of the benefits 
of sight as to be insensible to his misfortune, not 
conceiving that the lack of this sense very much 
impairs his pleasure ? Saunderson, who certainly 
deserves the name of philosopher, was not thus 
indifferent, and I doubt much whether he would have 
agreed with the author of the excellent Treatise on 
Systems ; I suspect the latter to have fallen into a 
"system" himself when he writes that, " had the 
life of man been only an uninterrupted sensation of 
pleasure or of pain, happy without prospect of pain, 
wretched without any prospect of pleasure, he would 
have rejoiced or suffered ; and that if he were so 
constituted, he would not have looked about him to 
discover if some influence were well disposed towards 
him, or desired to injure him ; it is only the alterna- 
tion between these two conditions which causes him 
to reflect," etc. 

Can you believe, madam, that by a clear train 
of reasoning (for that is the author's m.ethod of 
philosophising) he would ever have been led to 
this conclusion ? It is not with happiness and 
misery as with light and darkness ; the one is not 
simply the privation of the other. We might, 



THE LETTER ON THE BLIND 133 

perhaps, have entertained the idea that happiness was 
as essential to us as existence and thought, had we 
enjoyed it without intermission ; but I cannot say 
the same with regard to unhappiness. It would have 
been very natural to look on it as a forced condition, 
to feel oneself innocent, yet to believe oneself guilty 
and to accuse or excuse nature as at present. 

Does the Abbe de Condillac suppose that a child 
in pain only cries from his pain not having been 
without intermission from his birth? If he replies 
that "existence and pain would be one and indivis- ^i 

ible for one who had alwa>-s suffered, and that such y\, 
an one could not imagine cessation of suffering with- i> 

out cessation of his existence," I make repl)' : " The 
man living in continual misery possibly might not \ 
have said, 'What have I done that I should suffer I 
thus?' but why might he not have said, 'What '| 
have I done that I should be brought into being ? ' " 
At the same time, I see no reason why he should 
not have used his two synonymous verbs, I exist and 
I suffer^ the one in prose, the other in poetry, as ^ 
we use the two expressions, I live and I breathe. 
Moreover, madam, you will observe better than I 
do that this passage of the Abbe de Condillac's is 
admirably fine, and I fear you may say, after com- 
paring my criticism with his reflections, you prefer 
an error of Montaigne's to a truth of Charron's. 

You may blame my continual digressions. But 
digr essions are of the essence of this treatise. Now 
my opinion on the two foregoing questions is this : A 
the first time the eyes of one born blind ogeri_to the 



134 DIDEROT S PHILOSOPHICAL WORKS 

light, he will see nothing at all ; some time will be 
necessary for his eye to practise sight ; it will 
practise alone and without the aid of touch, and 
will eventually distinguish not only colours but the 
main outlines of objects. Supposing he acquired 
this aptitude in a very short space of time, or 
acquired it by using his eyes in the dark apartment 
in which he had been confined and urged to use that 
exercise for some time after the operation and 
before the experiments ; let us now see whether he 
would recognise at sight the bodies he had touched, 
so as to give them the proper appellations. This is 
the final question. 

In order to treat the question in the manner you 
will appreciate — for you like method — I will classify 
the persons on whom the experiment might be 
made. If they are dullards without education and 
knowledge and also unprepared, I hold that when 
the operation for cataract has completely removed 
the defect of the eye and the eye is in a healthy 
state, objects would be very distinctly pictured in 
it ; but such patients, being unaccustomed to any 
kind of reasoning and not knowing anything of 
sensation or idea, would be unable to compare the 
sensations they had received by touch with those 
they now receive by sight, and would at once 
exclaim, " There is a round,, there is a square," so 
that their judgment is not to be relied on ; or even 
the}' will possibly own that they saw nothing in the 
objects present to their sight like what they have 
handled. 



THE LETTER ON THE BLIND 135 

Another class there is, who by comparing the -*» 
forms they see with the bodies that had previously 
made~an~Tmpression upon their hands, and mentally 
applying touch to distant objects, would describe 
one body as a square, and another as a circle with- 
out well knowing why, their comparison of the ideas 
they have acquired b}' sight not being sufficiently 
distinct in their minds to convince their judgment. -^/I 

I pass to a third class of subject, a metaphysician. / 
He, I make no doubt, would, directly he began to / 
see objects clearly, reason as if he had seen these 
bodies all his life ; and after comparing the ideas 
acquired by sight with those acquired by touch he 
would declare as confidently as you or I : "I am 
very much inclined to think that this is the body 
which I have always called a circle, and that again 
what I named a square, but will not assert it to be 
really so. What is to prevent their disappearance 
if I were to touch them ? How am I to know 
whether the bodies I see are also meant to be 
touched? I do not know whether visible things are 
palpable ; but were I assured of this, and did I take 
the word of those about me that what I see is really 
what_I have touched, I should be no better off. 
These bodies may transform themselves in my hands 
and transmit on contact sensations quite different 
from those resulting from sight. " Gentlemen," 
would he conclude, ' ' this body appears to be the 
square, that the circle ; but that they are the 
same to touch as to sight is what I have no know- 
Ied|e of." 



136 DIDEROT S PHILOSOPHICAL WORKS 

If we take as our subject a geometrician instead 
of a metaphysician, he will likewise say of the two 
figures he has before his eyes, one is what he used 
to call a square, the other what he used to call a 
circle : " For I see," he would add, " that it is only 
in the former I could arrange my threads and insert 
my large-headed pins which denoted the angles of 
the square ; and only in the latter figure I could 
place the threads I required to demonstrate the 
properties of a circle. Here is a circle, then, and 
here is a square. But," he would have added with 
Locke, * ' perhaps when I lay my hands on these 
figures they will change one into another, so that 
the same figure would serve me in demonstrating 
the properties of a circle to the blind and the pro- 
perties of a square to the sighted. I might possibly 
see a square and at the same time feel a circle. No," 
he would have continued, " I am wrong. Those to 
whom I demonstrated the properties of the circle 
and the square had not their hands on my abacus, 
and did not touch the threads which I had stretched 
to outline my figures, and yet they understood me ; 
they therefore did not see a square when I felt a 
circle, otherwise we should have been at cross- 
purposes ; I should have been outlining one figure 
and demonstrating the properties of another, I 
should have given them a straight line for the arc of 
a circle, and an arc for a straight line : but as they 
all understood me, all men see alike : what they saw 
as a square, I see as a square ; what they saw as 
a circle, 1 see as a circle. So this is what I have 



THE LETTER ON THE BUND 137 

always called a square and that is what I have 
always called a circle." I have substituted a circle 
for a sphere and a square for a cube, because there 
is reason to think that we only judge of distances by 
experience ; and of course he who uses his eyes for 
the first time sees only surfaces without knowing 
anything of projection, since a projection consists in 
certain points appearing nearer to us than others. 

But even if the blind man were able in his first 
attempt to judge of the projection of solidity of 
bodies and distinguish not only a circle from a square 
but likewise a sphere from a cube, yet I do not 
therefore think that this will hold good with regard 
to the case of more composite bodies. There is reason 
to suppose that Monsieur de Reaumur's blind woman 
distinguished between colours, but the odds are thirty 
to one that what she said of the sphere and the cube 
was purely guesswork. I am firmly persuaded that 
it was not possible for her (without inspiration) to 
recognise her gloves, her dressing-gown, and her 
'sHoesT' These^bjects are so composite and full of 
detail ; there is so little resemblance between their 
total shape and that of the limbs they are designed 
to adorn or cover that Saunderson would have been 
infinitely more perplexed to find out the use of his 
mortar-board than d'Alembert or Clairaut to dis- 
cover the use of his tables. 

Saunderson would infallibly have supposed a 
geometrical relation between the object and its use, 
hence he would have recognised that his skull-cap 
was made for his head, for this had no arbitrary 



138 DIDEROT S PHILOSOPHICAL WORKS 

form to confuse him. But what would he have 
thought of the points and tassel of his mortar- 
board ? What was the use of the tassel, or why four 
points rather than six ? And these two ornamental 
peculiarities would for him have been the source of 
a number of absurd theories, or rather an excellent 
satire upon what we call good taste. 

Taking everything into mature consideration, 
it will be admitted that the difference between a 
person who has always seen, but to whom the use 
of an object is unknown, and one who knows the 
use of an object, but has never seen, is not to the 
latter's advantage. Yet, do you think, madam, if 
you were shown a head-dress to-day for the first 
time, you would ever guess it to be an ornament, 
and particularly intended for the head ? But if it 
be more difficult for one born blind and seeing for 
the first time to form a correct idea of complex 
objects, what is there to prevent him taking a 
person dressed and sitting motionless in an arm- 
chair for a machine or a piece of furniture, and a 
tree with its leaves and branches tossed by the 
wind for a self-moving, animated, and thinking 
being ? How much our senses suggest to us ; and 
were it not for our eyes how apt should we be to 
suppose that a block of marble thinks and feels ! 

It is certain, therefore, that Saunderson would 
have been assured of his not being mistaken in the 
judgment he had just given of the circle and the 
square, and that there are cases when the reasoning 
and experience of others are of value in elucidating 



THE LETTER ON THE BLIND 139 

the relation of sight to touch, and in teaching that 
what a thing is to the eye, it is Hkewise to touch. 
"~rf' would, however, be not the less essential in 
demonstrating some proposition of universal applica- 
tion (as it is termed) to test the proof by depriving 
it of the evidence of the senses ; for you are 
very well aware, madam, that if some person 
attempted to prove to you that two parallel lines 
seen in perspective are to be represented in a picture 
by two converging lines, because the two sides of 
an avenue appear to converge, it would be forgetting 
that the proposition is as true for one that is blind 
as for himself. But the foregoing supposition of 
one born blind suggests two others : firstly, of a 
.man who had always seen, but was devoid of the 
.sense of touch ; secondly, of a man in whom the 
senses of sight and touch were mutually contra- 
dictory. We might ask the former whether, if the 
missing sense were given him, or sight were obscured 
by a bandage, he would recognise bodies by touch. 
'It is clear that geometry (provided he were 
acquainted with that science) would be an infallible 
guide as to whether the evidence of the two senses 
were contradictory or no. All he would have to do 
would be to take the cube or sphere in his hand, 
and demonstrate its properties, and pronounce that 
what he feels a cube is a cube to the eye ; hence it 
is a cube he holds. As to one who is ignorant of 
this science, I believe he would not more easily 
distinguish a cube from a s])here by touch than 
Molyneux' blind man distinguished them by sight. 



I40 DIDEROT S PHILOSOPHICAL WORKS 

In the case of a man in whom the sensations of 
sight and touch are in a perpetual contradiction, I 
do not know what he would think of shapes, order, 
symmetry, beauty, ugliness, etc. In all probability 
he would be with regard to those things as we are 
with regard to the real extension and real duration 
of beings. He would, in general, say that a body 
possesses a shape, but he must be inclined to think 
that it is neither that which he sees nor that which 
he feels. Such an one might be dissatisfied with 
his senses, but his senses would be neither satisfied 
nor dissatisfied with the objects. Were he inclined 
to charge one sense with inaccuracy, I imagine it 
would be touch. A hundred circumstances would 
incline him to think that the form of objects changes 
rather by the action of his hands upon them than 
by that of the objects on his eyes. But in conse- 
quence of these preconceived notions, the difference 
between hardness and softness which he would find 
in bodies would be very perplexing to him. 

But does it follow that figures are better known 
to us because our senses are not self-contradictory ? 
Who has told us that they are not false witnesses ? 
Yet we pass judgment. Alas ! madam, when we 
weigh our human knowledge in Montaigne's scale, 
we are almost reduced to adopting his motto. For 
what do we know ? What of the nature of matter ? 
Nothing. What of the nature of spirit and thought ? 
Still less. What of the nature of movement, space 
and duration ? Absolutely nothing. What of the 
truths of geometry ? Ask any honest mathema- 



THE LETTER ON THE BLIND 141 

ticians, and they will own to you that all their pro- 
positions are identical, and that so many volumes 
upon the circle (for example) are nothing but 
repetitions by a hundred different methods that 
it is a figure where all the lines drawn from the 
centre to the circumference are equal. Thus we 
scarce know anything, yet what numbers of books 
there are whose authors have all pretended to know- 
led^! I cannot think why the world is not tired of 
reading so much and learning nothing, unless it be 
for the very same reason that I have been talking 
to you for two hours, without being tired and with- 
out telling you anything.^ 

With profound respect, 

I am, madam, 
Your very humble and obedient servant.^ 

' [This translalion has been collated with an eighteenth-century 
translation, undated and anonymous, entitled a Letter on Blindness.'\ 



ADDITION TO THE PRECEDING 
LETTER 1 

I AM going to jot down, anyhow, on paper, certain 
phenomena of which I was then ignorant, and which 
will serve as proofs or refutations of certain para- 
graphs in my Letter on the Blind. I wrote the latter 
thirty-three or thirty-four years ago, and I have re- 
read it without partiality, and am not entirely dis- 
satisfied with it. Although the first portion seemed 
to me more interesting than the second, and I felt 
that the former could have been further extended, 
the latter much abbreviated, I left both as I had 
written them, for fear that the young man's v.ork 
might suffer by the old man's retouching. I think 
I should find it impossible to-day to emulate all that 
passes muster in ideas and in expression : and I fear 
I am equally unable to correct what merits criticism. 
A famous contemporary painter spends the evening 
of his life in spoiling the master-pieces produced in 
his maturity. I know not if the defects he finds in 
them are real ; but either he never possessed the 

1 "We have appended to the Letter on the Blhid i\it sequel which 
Diderot composed a long time after it. . . . Those who accuse the 
writer of having always written hastily or of having always been hard 
and positive have certainly not read all his works. This sequel alone 
would confute them " — {Dcpping, B) 

142 



ADDITION TO THE PRECEDING 143 

talent to improve them if he carried the imitation 
of nature to the extreme limits of art ; or, if he 
possessed it, he has lost it, for all human qualities 
perish as a man decays. There comes a time when 
taste gives counsels which are recognised as just, 
but which we are unable to follow. 

It is the weakness of spirit arising from the 
knowledge of weakness, or laziness which is one 
of the results of weakness and want of spirit, which 
stands in the wa}- of a labour which would detract 
from the value of my work rather than improve it : 

Solve senescentem mature sanus equum, ne 
peccet ad extremum ridoidus^ et ilia ducat} 

Horace, Epistolar., lib. i, epist. i, v. 8, 9. 

Phenomena 

I. An artist who is both an enlightened student 
of the theory of his art, and unequalled in its practice, 
has assured me that it was by touch and not by 
si^ht that he judged of the soundness of kernels ; 
and that he rolled them gently between his thumb 
and first finger, and so discovered by successive im- 
pressions small inequalities of surface which were 
invisible to his eye. 

II. I have heard of a blind man who recognised 
by touch the colour of stuffs. 

III. I could name one who arranges the colours 
of bouquets with the taste upon which Jean Jacques 

' ' ' You would be wise to turn loose the old horse in good time, lest he 
fail in the end, amid laughter, and strain himself." 



144 DID E ROT'S PHILOSOPHICAL WORKS 

Rousseau prided himself when, whether in jest or 
earnest, he confided to his friends his scheme for 
setting up a school to teach the flower-sellers of 
Paris. 

IV. At Amiens there was a blind dresser who 
presided over numerous workmen as well as if he 
had the gift of sight. 

V. In the case of one sighted man the use of his 
eyes destroyed his certainty of touch ; and in order 
to cut his hair, he removed the mirror and placed 
himself before a bare wall. The blind man who 
does not see a danger that threatens hirn is the 
more courageous, and I am sure he would walk 
with firmer step over the narrow and elastic planks 
bridging a precipice. There are very few who are 
undismayed by the sight of abysses beneath them. 

VI. Everyone has heard of the famous surgeon 
Daviel. ^ I was often present during his operations. 
He removed a cataract from the eyes of a blacksmith 
who had contracted this disease from exposure to 
the fire of his forge ; and during twenty-five years 
of blindness he had grown so accustomed to the 
guidance of touch that he had to be forced to use 
the sense which had been restored to him. Daviel 
would beat him and say, "Use your eyes, you 
wretch ! " He walked and moved, and did all that 
we do with our eyes open, with his eyes shut. 

^ Jacques Daviel, surgeon, born in 1696. In 1728 he made a special 
study of diseases of the eye, and acquired such a high reputation for skill, 
that in the month of November 1752 alone he performed two hundred 
and twenty-six operations for cataract, of which one hundred and eighty- 
twu were successful. He died in 1762. —(A) 



ADDITION rO THE PRECEDING 145 

We are drawn to the conclusion that the eye is 
not so necessary nor so essential to our happiness 
as we are inclined to believe. If the spectacle of 
nature had no charms for the blind smith Daviel 
operated on, what object is there to the loss of which 
we should be otherwise than indifferent, after long 
deprivation of sight accompanied by no pain ? The 
sight of a beloved woman ? I don't believe it, in 
spite of the story I am going to relate. We imagine 
that if one had passed a long time without seeing, 
one would never be weary of looking ; but that is 
not the case. What a contrast between momentary 
andcpnstant blindness ! 

VII. Poor patients seeking Daviel's help were 
drawn to his laboratory from all the provinces of 
the kingdom by his charity, and his reputation also 
gathered there a large body of interested and learned 
spectators. I believe Marmontel and I were present 
on. the same day. The patient was seated and his 
cataract removed ; Daviel laid his hand upon the 
eyes which he had just restored to the light. An 
old woman, standing beside him, showed the liveliest 
interest in the success of the operation ; she shook 
in every limb at each movement of the operator. 
The latter aigned to her to draw near, placed her 
kneeling ce ^osite '^he patient, and removed his 
hands. The patient . ^^ned his eyes, saw, and 
cried : " Oh, it is my mou.^. ." I have never heard 
a more piteous cry ; I seem to hear it still. The 
old woman fainted, the spectators wept, and gave 
their montl/ freely. 

10 



146 DIDEROT'S PHILOSOPHICAL WORKS 

^^ VIII. The most astonishing case of all those who 
have lost their sight almost from their infancy was 
Mademoiselle Melanie de Salignac, a relative of 
Monsieur de la Fargue, a lieutenant-general in the 
army, who recently died at the age of ninety-one, 
covered with wounds and honours. She was the 
daughter of Madame de Blacy, who is still living, 
and who never ceases to regret a child who was the 
delight of her life and the admiration of all her 
acquaintances. Madame de Blacy is a woman of 
high character, who is willing to confirm the truth 
of my account. I write from her dictation such par- 
ticulars of the life of Mademoiselle de Sahgnac as 
did not come under my personal observation during 
a friendship which began with her and her family 
in 1760, and which lasted until 1763, the year of 
her death. 

She had a sound judgment and great sweetness 
of disposition and subtlety of mind, as well as naivete 
and freshness. When an aunt asked her mother to 
help her entertain nineteen bores at dinner, she 
replied, " I do not understand my dear aunt : why 
be kind to nineteen bores ? I only wish to be kind 
to those I love." 

The sound of voices had the same a ♦•' paction or 
antipathy for her as facial exp''"2:3lon pniose who 
see. A relation of hers, a r^ „iver-genei^ leof fiinaiice, 
unexpectedly behaved ' _iy to her famly, and she 
said with astonishment : " Who would hc.ve believed 
it of such a charming voice?" When she heard singers, 
she distinguished between dark d^ndfair '-^ices. 



ADDITION TO THE PRECEDING 147 

When. people spoke to her, she judged of their 
height by the direction of the sound, which came to 
her from above if the person speaking were tall, and 
from below if that person was short. 

She was not anxious to see, and one day I asked 
her the reason. " The reason," she replied, " is that 
then I should only have my own eyes, whereas now 
I have the use of everybody's ; by this loss I am 
always an object of interest and pity, at every in- 
stant people do me kindnesses, and at every instant 
I am grateful. Alas ! if I could see, no one would 
trouble about me. " 

The errors to which sight is liable diminished its 
value in her eyes. " I stand," she said, " at the 
entrance of a long alley ; and there is a certain 
object at its far end. One of my friends sees it 
moving, another sees it stationary ; one says it is 
an animal, another that it is a man ; and on approach- 
ing it, it turns out a tree-stump. No one can tell 
if the tower they see in the distance is round or 
square. I brave a whirlwind of dust, while those 
about me close their eyes and become ill — some- 
times for a whole day — because they had not shut 
their eyes soon enough. An imperceptible atom is 
enough to cause them cruel pain." At the approach 
of night she used to say that "our reign was draw- 
ing to a close, while hers was beginning." Living in 
the dark, and accustomed to act and think during 
this eternal night, insomnia, which is such a burden 
to us, had no terrors for her. 

She would not forgive me for my statement that 



148 DIDEROT S PHILOSOPHICAL WORKS 

the blind, to whom the symptoms of suffering are 
invisible, must be cruel. " Do you imagine," said 
she, ' ' that you hear a cry of pain as I do ? " " There 
are people," said I, " who suffer in silence. " "I 
believe," she said, " that I should soon discover them 
and pity them all the more." 

She was devoted to reading and passionately fond 
of music. " I think," said she, " I should never 
tire of hearing good singing or playing ; and if this 
were the only pleasure in heaven, I should not be 
sorry to go there. You are right in maintaining 
that music is the most impassioned of the fine arts, 
not excepting poetry and oratory ; that even Racine 
does not express himself as subtly as a harp, that 
his music is heavy and monotonous when compared 
with an instrument, and that you have often wished 
to give your style the strength and lightness of 
Bach's music. Music is the most beautiful language 
I know. In spoken language, the better we pro- 
nounce words, the more particularly we articulate 
each syllable ; whereas in the language of music, 
sounds of the most widely different pitch from bass 
to treble and treble to bass follow one another im- 
perceptibly, forming one single prolonged syllable, 
which varies its inflexion and expression at every 
moment. While this syllable is brought to my ear 
by the melody, the harmony carries it out, without 
any confusion, upon a number of instruments — two, 
three, four, or five perhaps — which all combine to 
strengthen the expression of the melody. I can 
understand the music without the words sung, if the 



ADDITION rO THE PRECEDING 149 

symphonist is a man of genius whose music is full of 
character and expression. Music is most delicious 
and expressive in the silence of night. 

" I fancy that people who see, distracted by their 
eyes, cannot listen and hear as I can. Why does 
the praise of music I hear seem poor and faint ? 
Why can I never speak of it as I feel ? Why do I 
pause in the midst of what I am saying, seeking 
vainly for words expressive of what I feel ? Are 
such words not invented ? I know nothing compar- 
able to the effect of music but the joy I feel when, 
after a long absence, I throw myself into my 
mother's arms ; my limbs tremble, my tears flow, 
and my knees totter, and 1 feel as if I should die 
of joy. " 

She had the most delicate feelings of modesty ; 
and when I asked her reason, she replied : " It is 
the result of my mother's teaching, who has so 
often told me that the sight of certain parts of the 
bady is an invitation to vice. I confess I have only 
understood her lately, and perhaps I had to become 
less innocent to do so." She died of an internal 
tumour of which she never had the courage to 
inform anyone. 

She was extremely neat and clean in her clothes 
and person, and this is the more remarkable as she 
had not eyesight to assure her that she had been 
successful in avoiding the vice of uncleanness and 
untidiness. 

When her glass was being filled, she knew by the 
sound of the liquid as it fell, when it was full. She 



ISO DIDEROT S PHILOSOPHICAL WORKS 

fed herself with surprising dexterity. Sometimes 
she amused herself by standing before a mirror to 
dress herself, and by imitating all the affectations of 
a coquette. The mimicry was so true to life that 
we laughed aloud. 

From her earliest youth efforts had been made to 
train her other senses, and the results were astonish- 
ing. Touch enabled her to discern minute details 
in shapes of objects which often pass unnoticed by 
those who have the best eyesight. 

She had very delicate senses of hearing and smell ; 
she knew by the feeling of the air whether the 
weather was cloudy or fine, whether she was walk- 
ing in a square or a road, in a road or a cul-de-sac, 
in an enclosed or open place, in a vast apartment 
or a small room. She measured the space by the 
sound of footsteps or the echo of voices. When 
she had gone over a house, its plan remained in 
her head, so that she would warn others of little 
obstacles or dangers in their way. " Take care," 
she would say, " the doorway here is low ; you will 
find a step there." 

She noticed a variety in voices which we have no 
conception of, and when she had heard a person 
speak once or twice she knew him for ever. 

She was very little affected by the charms of 
youth and by the wrinkles of age ; and said she 
was only charmed by the fine qualities of the heart 
and intellect — one of the advantages of the loss 
of sight, especially for women. " My head will 
never," she said, " be turned by a handsome face." 



ADDITION TO THE PRECEDING 151 

She had a very trusting disposition. It was so easy, 
and would have been so shameful, to deceive her. 
To lead her to imagine she was alone in a room, 
when this was not so, would have been the blackest 
gfjtreacheries. 

She was never subject to panic, and rarely to 
ennui ; for she had learnt in her solitude to be 
independent of others. She noticed that at night- 
fall in travelling in public vehicles people became 
silent. " I do not need," she said, "to see those 
whom I love to converse with." She set the 
greatest value upon sound judgment, sweetness of 
disposition, and gaiety. She spoke little, and was 
an excellent listener. " I am like the birds," she 
said : " 1 learn to sing in the dark." 

When she compared what she heard from day 
to day, she was astonished at the contradictor}' 
nature of our opinions ; praise or blame seemed to 
her a matter of indifference from such inconsistent 
creatures as human beings. 

She had been taught to read by cut-out letters. 
She had a pleasant voice, and sang with taste, and 
would have gladly spent her life at concerts or 
operas ; the only music she did not care for was 
noisy music. She danced exquisitely, and also 
played the viol very well, and owing to this talent 
she was greatly in demand among young persons 
of her age, to whom she taught the fashionable 
dances. 

She was the best beloved of her brothers and 
sisters. " You see," she siaid, "what I owe to my 



152 DIDEROT S PHILOSOPHICAL WORKS 

infirmities ; people become attached to me as a 
result of their kindness to me, and of my efforts to 
show my gratitude and deserve their good offices. 
Besides, my brothers and sisters are not jealous. 
If I had sight, my heart and intellect would be the 
losers. I have so many inducements to be good ! 
What would become of me if I were to lose the 
interest that I inspire ? " 

In her parents' loss of fortune, the only thing she 
regretted was the loss of her masters ; but the)' had 
so much liking and esteem for her that her music 
and mathematical masters begged her to let them 
teach her for nothing. She asked her mother : 
"Mother, what am I to do ? They are not rich, 
and need all their time." 

She had been taught music by notes in relief 
placed on raised lines on a large board. She read 
these notes with her hand, and played them on her 
instrument, and in a very short time she learnt to 
play the longest and most elaborate piece. 

She knew the elements of astronomy, algebra, and 
geometry. Her mother, who read her Abbe de la 
Caille's book, would now and again ask her if she 
understood it. " Quite easily," she would reply. 
^;^><1 She declared that geometry was the science of the 
blind, because it was of such universal application 
and no external aid was necessary to become pro- 
ficient in it. "The geometrician," she added, 
"spends nearly all his life with his eyes shut." 

I have seen the maps with which she studied 
geography. The parallels and meridians were made 



ADDITION TO THE PRECEDING 153 

of wire ; the boundaries of kingdoms and provinces 
of embroidery in linen, silk, or wool of various thick- 
ness ; the rivers and streams and mountains of pins' 
heads of various sizes ; and cities and towns of drops 
of wax of various sizes. 

One day I said to her, " Mademoiselle, imagine 
a. cube." 

"1 see it." 

" Place a point in the centre of the cube." 

" I have done so." 

" From the point draw straight lines to the angles ; 
into what have you divided the cube ? " 

"Into six pyramids," she replied without hesita- 
tion, "each having as its base one side of the cube, 
and a height equal to half its height." 

' ' True, but tell me where you see this ? " 

" In my head, as you do." 

I must admit I have never been able clearly to 
understand how she represented figures in her head 
without the aid of colour. Was her cube formed 
from memories of sensations of touch ? Had her 
brain become, as it were, a hand within which sub- 
stances were realised ? Had a connection between 
two senses been established ? Why does this con- 
nection not exist in my case, and why do I picture 
nothing that is not coloured in my mind's eye ? 
What is the imagination of a blind man ? This 
phenomenon is by no means easy of explanation. 

She wrote with a pen, with which she pricked a 
sheet of paper stretched on a frame divided by two 
parallel and movable slats, which only left sufficient 



154 DIDEROT'S PHILOSOPHICAL WORKS 

space between them for one line of writing. The 
same method of writing served to answer her, as she 
read the communication by passing her finger-tips 
over the slight roughness formed on the back of the 
paper by the needle or pin. 

She read books printed on one side of the paper 
only for her use by Prault. One of her letters was 
printed in the Mercure. 

She took the trouble to copy out with her needle 
President Henault's Historical Synopsis,^ and her 
mother, Madame de Blacy, gave me this curious 
document. 

People will find it difficult to accept the following 
fact, though I and all her family, as well as twenty 
persons still alive, can vouch for it. Given a piece 
of poetry of twelve to fifteen lines, if she was told 
the first letter and the number of letters in each 
word, she could reconstruct the poem, however odd 
and far-fetched. I tried her with Colle's ^ ambigouris. 
She sometimes lighted on a better word than the 
original. She threaded the finest needle rapidly by 
laying the thread or silk on the index finger of her 
left hand and drawing this with a fine point through 
the eye of the needle placed perpendicularly. She 
could make all sorts of small articles — edgings, bags 
of all kinds, some of drawn work, and of various 
patterns and colours ; garters, bracelets, necklaces 
made of glass beads the size of letters arranged to 



' \^Abr^gt' de Phistoire de France.'] 

- [Colle, Charles (i 709-1783), a dramatic author who also wrote 
ambis^oiiris or nonsense verses.] 



ADDITION TO THE PRECEDING 155 

form patterns. I am sure she would have made a 
good compositor, for the greater includes the less. 

She played reversis, mediaieur, and quadrille well. 
She sorted her cards herself, and recognised each by 
touch from minute peculiarities others could neither 
see nor feel. In reversis she had a special place for 
the ace (especially the ace of diamonds) and the 
knave of hearts. The only difference in playing 
with her was that the card played was named. If 
the 'knave of hearts was in danger, a smile passed 
over her face, which she could not restrain though 
she realised that it was indiscreet. 

She was a fatalist, and believed that our efforts -^<:^^ 
to escape our destiny only served to draw us thither. 
I do not know what she thought of religion ; she 
kept her opinions to herself out of consideration for 
her mother, who was devout. 

Lastly, I will give you her ideas upon hand- 
writing, drawing, engraving, and painting, and they 
are, I think, very just, as I ho[)c )'ou will think after 
reading the following conversation between us. She 
begins the dialogue : 

" If you trace on my hand with a point, a nose, 
a mouth, a man, a woman, or a tree, I should be 
sure to recognise them ; and if the tracing W3s 
correct, I should hope to recognise the person whom 
you had drawn ; my hand would become a sensitive 
rnirror, but the difference in sensibility between this 
hand and the organ of sight is immense. I suppose 
the eye is a living canvas of infinite delicacy ; the 
air strikes the object, and is reflected back from the 



156 DIDEROT'S PHILOSOPHICAL WORKS 

object to the eye, which receives a multitude of im- 
pressions varying in accordance with the nature, the 
form, the colour of the object, and also perhaps 
with the properties of the air which I do not know, 
and of which you are equally ignorant ; and the 
object is represented to you by the variety of these 
sensations. 

"If the skin of my hand was as sensitive as your 
eye, I should see with my hand as you see with your 
eyes ; and I sometimes imagine there are animals 
who have no eyes, but can nevertheless see." 

' ' And the mirror ? " 

" If any bodies are not mirrors, it is by some 
defect in their composition which destroys the re- 
flection of the air. I think this is the more likely 
as gold, silver, iron, and copper, when polished, are 
able to reflect the air, while rough water and cracked 
ice lose this property. Variety in sensation (and 
hence in the property of reflecting air), in the 
materials you employ, distinguishes the w^riting 
from the drawing, the drawing from the engraving, 
the engraving from the picture. The writing, the 
drawing, the engraving, and the picture in one colour 
are all monochromes." 

"But if there is only one colour, we should only 
distinguish that colour." 

"It seems that the surface of the canvas, the 
depth of colour, and the way in which it is used, 
produce in the reflection of the air a corresponding 
variation to that of the objects. Don't ask me any 
more, for that is all I know\" 



ADDITION rO THE PRECEDING i57 

" To try to teach you any more would be waste 
of time." 

I have not described in her case all I might have 
noticed if I had seen her oftener and questioned her 
skilfully. I give you my word of honour that all I 
have recorded is actual fact. 

She died at the age of twenty-two. With a 
wonderful memory, and strength of mind as wonder- 
ful, what progress she would have made in science 
if she had had a longer Hfe ! Her mother read 
history to her, and this was a task pleasant and 
useful to both of them. 



LETTER ON THE DEAF AND DUMB 

Letter to Monsieur 

2Qth Jan. 175 1. 
I AM sending, sir, to the author of The Fine Arts 
reduced to a Single Principle^ the Letter revised, 
corrected, and augmented in accordance with the 
advice of my friends ; but always with the same 
title. 

I grant that this title is applicable equally to the 
large number of those who speak without under- 
standing and the small number of those who under- 
stand without speaking, and to the very small number 
of those who speak and understand, and for whose 
use my letter is solely intended. 

I admit that it is an imitation of another Letter^ 
which might be better ; but I am tired of hunting 
for a better title. Whatever importance you attri- 
bute to the choice of a title, the title of my letter 
will remain unchanged. 

I do not like quotations, and I like Greek quota- 
tions least of all ; they give a learned air to a book, 
which is no longer fashionable. They frighten away 
readers, and if I was deciding from a publisher's 

^ Letter on the Blind, for the Use 0/ those luko See. — (D) 
15S 



LETTER ON THE DEAF AND DUMB 159 

standpoint I should leave out such scarecrows. But 
I am not a publisher, so please suffer the Greek 
quotations to remain where I have placed them. If 
you care less for a book being good, than that it 
should be read, I do not agree with you ; what I care 
for is to make a good book, although it may risk 
being less read. 

As to the number of subjects I touch upon moving 
from one to another, I would have you know, and 
tell others, that this is no fault in a letter where 
one is allowed to converse freely, and where the 
last word of a phrase is a sufficient link to the 
next. 

You may therefore print me, if that is all ; but 
print me anonymously, if you please. I can always 
admit the authorship later. I know one to whom 
people would not attribute it, and another on whom 
it would be certainly fathered, if it possessed some 
eccentricity in its ideas, some share of imagination, 
style, some temerity of thought which I should be 
sorry to share, a fine display of mathematics, meta- 
physics, Italian and English ; less Latin and Greek, 
and more music. 

See that no errors creep into the text ; a single 
mistake is enough to ruin all. You will find in 
Havercamp's fine edition of Lucretius in the last 
book the figure I want. Take out the child which 
half hides her, imagine a wound beneath the breast, 
and have it copied. My friend Monsieur de S. has 
undertaken to revise the proofs. His address is . . . 

I am, etc. 



i6o DIDEROT'S PHILOSOPHICAL WORKS 

LETTER ON THE DEAF AND DUMB 

FOR THE USE OF THOSE WHO 

HEAR AND SPEAK : 

Which treats of the origin of inversio?is in language, of 
harmony of style, of sublimity of situation, and of some advan- 
tages which the French language has over most ancient and 
modern languages, also some thoughts on expression 
in the fine arts. 

I 'HAD no intention, sir, to take credit for your 
researches, and you may claim what you please in 
this letter. If it happens that my ideas are similar 
to yours, I am like the ivy which mingles its foliage 
with the oak. I might have addressed my letter to 
the Abbe de Condillac, or to Monsieur du Marsais, 
who has also treated of inversions ; but you just 
came to my mind, and I have made free with you, 
for I am persuaded that the public will not this 
time take a happy accident for a deliberate choice. 
My only fear is, that I may waste your time and 
snatch from you those hours which you are doubt- 
less devoting to philosophy, and which you owe 
to that study. 

Now, in order to treat of inversions we must first 
consider how languages are formed. Objects that 
strike^ the senses are those that are first noticed, and 
those which unite various qualities which strike the 
senses are named first, i.e. the different objects ot 
which the world is composed. Then the various 
qualities are distinguished and named, and these form 
most of our adjectives. Afterwards, these sensible 



LETTER ON THE DEAF AND DUMB i6i 

qualities being put aside, some common quality was 
observed in various objects, such as impenetrability, 
extension, colour, shape, etc., and from these abstract 
and general names were formed and nearly all sub- 
_stsUitiv^s. Gradually men became accustomed to 
think that all these names represented real things ; 
and the sensible qualities were regarded as simple 
accidents, and thus the adjective was thought to be 
subordinate to the substantive, although the sub- 
stantive does not really exist and the adjective is 
everything. If you are asked to describe an object, 
you answer that it is a body with a surface, im- 
penetrable, shaped, coloured, and movable. But 
subtract all these adjectives from your definition and 
what. is left of that imaginary being you call a body ? 
If you wished to arrange the terms of your definition 
in their natural order, you would say a coloured, 
shaped, extended, impenetrable, movable substance. 
It seems to me that a man seeing the object for the 
first time would be affected by the different qualities 
in this order of terms. The eye would be first 
struck by the shape, colour, and surface ; touch 
would then discover its impenetrability, and eye and 
touch together would discover its mobility. There 
would, therefore, be no inversion in this definition, 
and there is an inversion in the definition in its first 
form. It follows, therefore, that if we wish to 
maintain that there is no inversion in the French 
language, or at least that it is much' rarer than in 
the learned tongues, the utmost we can say is 
that our constructions in Trench are for the most 

II 



i62 DIDEROT'S PHILOSOPHICAL WORKS 

part uniform ; that the substantive is always, or 
nearly always, placed before the adjective ; and 
the verb between them. For if we consider the 
question on its own merits, and ask if the adjective 
should be placed before or after the noun, it will 
appear that we frequently reverse the natural order 
of ideas. The example I have just given is an in- 
stance of this. I say the natural order of ideas ; 
for we should distinguish here between the natural 
order and the acquired, or what we may term the 
SLientific order ; the latter is a deliberate arrange- 
ment after a language is fully formed. 

As adjectives usually represent sensible qualities, 
they stand first in the natural order of ideas ; but 
to a philosopher, or rather to philosophers who 
are accustomed to regard abstract substantives as 
realities, substantives will come first in the scientific 
order, being, in their language, the support which 
upholds the adjective. Thus of the two definitions 
of a body I gave, the first follows the scientific or 
acquired, the second the natural order. 

From this we may conclude that it is perhaps 
owing to the peripatetic philosophy, which realised 
all general and abstract entities, that we have in our 
language hardly any of what we call inversions in 
the classics. Our Gallic authors had much more 
than we have, and this philosophy was in the 
ascendant while our language was being perfected 
under Louis XIII and Louis XIV, The Ancients, 
who generalised less, and who studied nature more 
in detail, were less monotonous in the order of their 



LETTER ON THE DEAF AND DUMB 163 

tongue, and the word inversion would have perhaps 
astonished them. You will not raise as an objection 
here, that the peripatetic philosophy is Aristotle's 
philosophy, and hence the philosophy of some 
portion of the Ancients, for you doubtless tell your 
disciples that our peripatetic philosophy is very 
different from Aristotle's. 

But it is, perhaps, unnecessary to go back as far 
as the creation of the world and the origin of 
language to explain why inversions crept into and 
were preserved in languages. It would be sufficient 
to make an imaginary journey to a people whose 
language one was unacquainted with ; or, what 
comes to almost the same thing, to experiment with 
a man who would forgo the use of articulate sounds 
and try to make himself understood by gestures 
alone. Such a man, who would perfectly understand 
the questions put to him, would be an excellent 
subject for experiment ; and from the succession of 
his gestures definite inferences could be drawn as to 
the order of ideas which seemed good to the early 
men in order to communicate their thoughts by 
gestures, and under what circumstances articulate 
sounds were invented 

I should give my "theoretical mute" plenty of 
time to compcxse his replies ; and as to the questions, 
1 would make a point of introducing ideas whose 
expression by means of gesture I should be most 
anxious to learn. It would be both useful and 
entertaining to multiply experiments upon these 
ideas, and to propound the same questions to a 



164 DIDEROT S PHILOSOPHICAL WORKS 

number of persons at once. I believe that a philo- 
sopher who practised such experiments with some 
friends, who were intelligent men and good logicians, 
would not find it a total waste of time. An Aristo- 
phanes would no doubt turn it to ridicule, but what 
matter ? One could .say what Zeno said to his dis- 
ciple : el (JiiXocrocpla^ €7riduiui.ei^, irapaaKeva^ov auroOei^, 
0)9 KarayeXaOijcro/j.ei'o^, oog, etc. If you wish to become 
a philosopher, expect to be ridiculed. That is a fine 
maxim, sir, and one that would elevate souls less 
courageous than ours above human comment and all 
frivolous considerations. 

You must not confuse the experiment 1 suggest 
with ordinary pantomime. To translate an action 
and a speech into gesture are two very different 
things. I am sure that there are inversions in the 
language of our mutes, that each one has his style, 
and that their inversions denote differences as pro- 
nounced as those we find in ancient Greek and Latin 
authors. But as we always most highly approve of 
our own style, the discussion that would ensue after 
these experiments would be of the most lively and 
philosophical nature, for all our theoretical mutes, 
when they had leave to use their tongues again, 
would be obliged to justify not only their expres- 
sion, but also the way they placed such and such an 
idea in a certain order in their gestures. 

This leads me to another idea that is a little alien 
to the subject of my letter, but in a letter digres- 
sions are allowed, especially when they lead to 
useful results. iMy idea would be to analyse, as it 



LETTER ON THE DEAF AND DUMB 165 

were, a man, and to examine what he derives from 
each of his senses. 1 have sometimes amused 
myself with this kind of metaphysical anatomy, and 
I consider that of all the senses the eye was the 
most superficial, the ear the proudest, smell the 
most voluptuous, taste the profoundest and most 
philosophical. It would be amusing to get together 
a society, of which each should have only one 
sense ; there can be no doubt that all these persons 
would look on one another as out of his wits, and 
I leave you to judge with what reason. And yet 
this is an example of what happens amongst us 
every day ; we have, so to speak, only one sense, 
and we judge of everything. We may remark that 
this group of five persons, each possessing only one 
sense, might by their faculty of abstraction have 
one interest in common — that of geometry, — and 
might understand one another on that subject, and 
that alone. But to return to our theoretical mutes, 
and to the questions we should put them. 

If these questions were such that more than one 
answer was possible, it would follow that one mute 
would give one, and another mute another ; and 
that the comparison between their replies would 
become impossible or at any rate difficult. This 
difficulty suggested to me that a speech for transla- 
tion from French to gesture-language would be 
better than a question for experimental purposes. 
The translators must be warned to avoid ellipsis, for 
the language of gesture is difficult enough without 
increasing its laconism by the use of this figure. 



1 66 DIDEROT'S PHILOSOPHICAL WORKS 

By the efforts of those born deaf and dumb to 
make themselves understood, we see the)' express 
all they are able to express. I should therefore 
recommend our theoretical mutes to copy them, 
and, as far as is possible, to form no sentence where 
the subject and the attribute with all their depen- 
dencies are not expressed. In short, they would 
only be allowed the choice of the order in which 
they would present ideas, or rather the gestures 
representing these ideas. 

But there I see a difficulty. As thoughts, I 
know not by what contrivance, enter our mind very 
much in the form in which they appear in speech 
when they are tricked up, it is possible that this 
will cause some difficulty to our theoretical mutes ; 
perhaps they would be tempted to imitate the 
order of the words in the spoken language the>" are 
already familiar with — a temptation which assails 
almost everyone who writes in a foreign language. 
All of our best modern Latinists fall into French 
constructions, so that perhaps our mutes' construc- 
tion will not be the construction of a man who had 
never had any notion of speech. What do you say ? 
Perhaps this difficulty would be of less frequent 
occurrence if our theoretical mutes were philosophers 
or orators ; but if this obstacle arises we might have 
recourse to one born deaf and dumb, 
j/ You will doubtless think this a singular way 
of obtaining true notions of the formation of a 
language. But pray consider, how much less far 
from truth ignorance is than prejudice, and that a 



LETTER ON THE DEAF AND DUMB 167 

man born deaf and dumb has no prejudices with 
regard to the manner of communicating his thoughts. 
Consider that inversions have not passed into his 
language from another, and that if he uses them it 
is nature alone which suggests their use ; that he 
is closely analogous to those beings people have 
imagined who with no trace of education, very few 
perceptions, and almost no memory, might easily 
pass for two-footed or four-footed animals. 

I can assure you, sir, that a translation of this 
gesture language would do the translator great 
credit, for not only must he have completely under- 
stood the meaning and the thought, but the order 
of the words of the translation must faithfully follow 
the order of the gestures of the original. (To do 
this a philosopher would have to question his 
author, hear his replies, and represent them with 
exactness ; but philosophy is not learnt in a day.) 
One of these requisites would, however, facilitate 
the rest ; and if the question was given with a precise 
explanation of the gestures which are to compose 
the answer, it would be possible to represent ges- 
tures as far as possible by words. I say as far as v 
possible, for there are gestures so sublime that the | 
noblest eloquence can never translate them. Such \ 
is the scene in Shakespeare's tragedy of Macbeth. 
Lady Macbeth, walking in her sleep, advances 
silently with closed eyes (Act v, Scene i), and 
rubbing her hands together as if she were washing 
away the stain of the king's blood she had shed 
twenty years before. I know nothing in speech so 



1 68 DIDEROT S PHILOSOPHICAL WORKS 

pathetic as the silence and motion of this woman's 
hands. What an expression of remorse ! 

The way in which another woman carried the 
tidings of his death to her husband, who was still 
uncertain of his fate, is another example of a 
gesture unapproached in its vigour by the spoken 
word. She went with her son in her arms to a 
spot in the country which her husband could see 
from the tower in which he was imprisoned ; and, 
after looking for some time at the tower, she took 
a handful of earth which she scattered in the form 
of a cross on the body of her son, whom she had 
laid at her feet. Her husband understood the 
siern, and starved himself to death. The sublimest 
thought is forgotten, but these actions are never 
effaced from one's memory. I could make many 
reflections at this point on sublimity of situation, 
but they would take me too far from my subject. 

Many of the fine lines in that magnificent scene 
in Heraclius, where Phocas does not know which of 
the two princes is his son, have been justly admired. 
For my part, the passage in the scene that 1 prefer 
is that where the tyrant turns to each of the princes 
in turn, and calls them by the name of his son, and 
they both remain cold and motionless : — 

" Martian, a ce mot aucu)i tie vent repondre.'^'^ 

This cannot be put upon paper, and gesture here 
triumphs over speech. 

Epaminondas, at the battle of Mantinaea, is 

1 ["Martian! and none will answer to the word.'' — Corneille, 
Heracliiis, Act iv, Scene iv.] 



LETTER ON THE DEAF AND DUMB 169 

mortall)' wounded ; the doctors tell him he will 
die when the spear is drawn from his bod}\ He 
asks for his shield, for it is dishonourable to lose the 
shield in battle ; and when this is brought to him, 
he draws out the spear-head himself. In the sublime 
scene at the close of the tragedy of Rhodogune, the 
most effective moment is certainly when Antiochus 
lifts the bowl to his lips, and Timagene enters crying 
" Ah, lord !" (Act v, Scene iv). What a throng of 
ideas and emotions crowd upon the audience at this 
gesture and this cry ! But I am digressing. To 
come back to our man born deaf and mute. I know 
of one who would be useful for experimental purposes, 
because he is intelligent and has expressive gestures, 
as you shall see. 

I I was playing chess one day, and the dumb man 
was watching. My opponent fought me to a difificult 
position, and the dumb man quite understood, and, 
thinking the game was lost, he closed his eyes, 
drooped his head, and let fall his arms — as a sign 
that he considered me checkmated, or done for. 
Consider for a moment how metaphorical is the 
language of gesture. At first I thought as he did ; 
but as I had not exhausted the combinations, I was 
in no hurry to yield, and I looked about for a way 
out. The dumb man still thought there was none, 
and he expressed this very clearly by shaking his 
head and by putting back the lost pieces in the box. 
His example induced the other spectators to discuss 
the situation ; they examined it, and, after some 
fruitless expedients had been tried, a successful one 



170 DIDEROT S PHILOSOPHICAL WORKS 

was discovered. I made use of it, and explained to 
the dumb man that he was mistaken, and that I had 
escaped though he did not expect me to. But he, 
by pointing his finger at the spectators one after 
another, and making a motion of the Hps, accom- 
panied by a sweeping movement of his arms in the 
direction of the door and the tables, replied that it 
was no credit to me to have got out of my difficulty 
by calling in all and sundry to my help. His 
gestures were so significant that no one could mis- 
understand him, and the popular expression "all 
and sundry " ^ occurred to many at the same time : 
this expression was definitely translated by our 
dumb man's gestures. 

You know, at least you have heard, of a singular 

t machine with which the inventor proposed to give 

ii sonatas in colour. I thought that if anyone could 

|l appreciate a performance of ocular music, and could 

judge of it without prejudice, it would be a man 

born deaf and dumb. I therefore took my friend 

to the house in the rue St Jacques, where the 

operator and the machine with colours was exhibited. 

Ah, sir, you would never guess the kind of impression 

that it made on him, nor the ideas it suggested. 

You see that it was impossible to explain to him 
beforehand the nature and marvellous powers of the 
harpsichord ; and, having no idea of sound, this instru- 
ment with colours could not suggest to him any 
musical impressions. The purpose of the machine 

' \ConsuUer le tiers^ le quart et les passants ; literally, "the third, 
the ijuarter, and the passers-by.''] 



LETTER ON THE DEAF AND DUMB 171 

was as incomprehensible to him as the use of our 
organs of speech. What, then, were his thoughts, 
and what was the cause of his admiration for Father 
Castel's coloured fans ? Guess, sir, his conjectures 
about this ingenious machine,^ which very few people 
have seen, though many have talked about it, and 
whose invention would do honour to many of those 
who ridicule it. Our deaf-and-dumb friend imagined 
that the inventor was also deaf and dumb, and that 
his harpsichord was the instrument by which he com- 
municated with other men ; he imagined also that 
each shade of colour represented a letter of the 
alphabet, and that by touching the keys rapidly he 
combined these letters into words and phrases, and, 
in fact, spoke in colours. 

You may imagine he was pleased with his own 
perspicacity in finding this out ; but our friend did 
not rest on his laurels ; the idea suddenly came into 
his head that he now grasped what music and musical 
instruments were. He supposed that music was a 
peculiar manner of communicating thought, and that 
musical instruments — lutes, violins, and trumpets — 
were so many different organs of speech. You will 
say that only a man who had never heard music or 
a musical instrument could have happened on such 
a theory. But please consider that this theory, 
although obviously false to you, seemed almost 
proved to a deaf-and-dumb person. When the deaf- 



' [Voltaire ridiculed the machine invented by the Jesuit Caste). 
Diderot, on the other hand, returned to the idea ngain and again, 
and mentions it in the Encyclot>adia. — (A)] 



172 DIDEROT S PHILOSOPHICAL WORKS 

and-dumb man calls to mind the attention he has 
observed us pay to music and to musicians, and the 
evidences of joy or grief depicted on our countenances 
and in our gestures as we listen to beautiful music, 
and when he compares them with the similar effects 
, produced by speech or by visible objects, he cannot 
imagine that music has no definite meaning and that 
vocal and instrumental music arouses in us no distinct 
impressions. V 
/ And is not this, sir, an exact symbol of the way 

^^ which we form ideas, our theories, and, in a word, 
the conceptions by which so many philosophers have 
won fame ? Whenever they attempt to explain 
matters which seem to demand another organ which 
is lacking before they can be completely understood, 
they have often shown less penetration and have 
wandered further from the truth than the deaf mute 
I have been describing ; for, after all, if we do not 
express our thoughts as distinctly by means of 
musical instruments as with our lips, and if musical 
notes do not convey our ideas as distinctly as speech, 
yet they do convey something. 

The blind man I described in the Letter on the 
Blind'^ assuredly displayed great penetration in his 
conception of the use of the telescope and spectacles, 
and his definition of a mirror is very remarkable ; 
but there is more profundity and truth in my deaf- 
mute's notion of Father Castel's harpsichord and of 
our music and musical instruments. Even if he did 
not hit upon the exact truth, he hit upon a great 
^ See Letter on the Blind, pp. 72-73. 



LETTER ON THE DEAF AND DUMB 173 

possibility. »^his penetration will surprise you less, 
perhaps, if you fancy that everyone who walks 
through a picture gallery is really unconsciously 
acting the part of a deaf man who is amusing him- 
self by examining the dumb who are conversing on 
subjects familiar to him. This is one of the points 
of view with which I always look at pictures ; and I 
fancy it a sure means of divining ambiguous actions 
and equivocal movements ; of being at once aware 
of the frigidity and confusion of an ill-arranged 
action or of conversation ; and of seeing at once, 
in a scene rendered in painting, all the faults of 
languid or exaggerated acting. The term " acting " 
which I have just used, because it expresses what I 
mean, calls to my mind another mode of studying 
which I often employed and which taught me more 
about actions and gestures than all the books in the 
world. 1 used to frequent the theatre, and 1 knew 
by heart most of our best plays. On the days 
when I meant to examine actions and gestures I 
would climb to the gallery, for the further I was 
from the actors the better. As soon as the curtain 
was raised, and the rest of the audience disposed ; 
themselves to listen, I put my fingers in my ears, \ 
much to the astonishment of my neighbours ; not 
knowing my motives, they looked on me as a 
madman who only came to the play to miss it, I 
paid no attention to their remarks, and kept my 
fingers obstinately in my ears as long as the 
gestures and actions of the actor corresponded with 
the dialogue which I remembered. When I was 



174 DIDEROT'S PHILOSOPHICAL WORKS 

puzzled by the gestures I took my fingers from my 
ears and listened. Ah, how few actors there are 
who can stand such a test, and how humiliated the 
majority would be if I were to give the world my 
criticisms ! But judge of my neighbours' surprise 
when they saw me shed tears at the pathetic 
passages, though I had my fingers in my ears. 
That was too much for them, and even the least 
inquisitive began to question me. But I coolly 
\ answered that "everybody had his own way of 
II listening, and mine was to shut my ears to hear the 
' better," and found some silent amusement in the 
comments caused by my real or apparent eccen- 
tricity and in the simplicity of some young people 
who also tried putting their fingers in their ears to 
hear as I did, and were surprised at their lack of 
success. 

Whatever you may think of my expedient, pray 

consider that if, to judge correctly of intonation, 

I we must listen to an actor without looking at him, 

I it is very natural to watch an actor without hear- 

j ing him, if we are to judge correctly of his gestures 

I and action. I may add that the celebrated writer 

of plays, Le Sage, the author of TJie Lame Devil, 

The Bachelor of Salaina7ica, Gil Bias of Santillana, 

Turcaret, and a number of plays and comic operas 

in which his son, the inimitable Montmeny, took 

part, became so deaf in his old age that people had 

to shout into his ear-trumpet. Yet he was in the 

habit of frequenting the theatre to see his pieces 

played, and could follow them almost word for 



LETTER ON THE DEAF AND DUMB 175 

word ; indeed, he said he was a better judge of his 
plays and their action when he could no longer hear 
the actors ; and I am certain, from my own personal 
experience, that he was right. 

In studying gesture language it appears to me h 
the principal idea should be presented first, because \\ 
it throws light on the rest as indicating what the " 
succeeding gestures refer to. When the subject of 
a proposition in oratory or gesticulation is not 
announced, the significance of the other gestures or 
words remains uncertain. This is certainly the case \ 
in Greek or Latin phrases, but not in the language ' 
of gesture when properly constructed. Suppose I am ' 
at table with a deaf-mute, and he wishes to tell his 
servant to give me some wine. He first beckons to 
his servant, then looks at me, then he imitates the 
action of a man pouring out wine. In this sentence 
it hardly matters which of the last two signs comes 
first : the deaf mute, after beckoning to his servant, 
may either begin with the sign representing his 
order or that denoting the person whom the order 
concerns ; but the position of the first gesture 
cannot be altered. Only an illogical mute could 
displace it. For this displacement would be as 
absurd as a man speaking without knowing whom 
he was addressing. As to the order of the two 
other gestures, it is a matter of taste, fancy, 
suitability, and harmony of style, and does not 
afTect the sense. As a rule, the more ideas there 
are in a sentence, and the more possible arrangement 
of gestures or other signs there are, the greater 



1/6 DIDEROT S PHILOSOPHICAL WORKS 

danger of falling into contradictions, ambiguities, 
and other faults of construction, 1 do not know if 
we can justly estimate a man's opinions and morals 
by his writings, but 1 think we can form a good 
judgment of his intellectual abilities from his style, or 
rather his manner of constructing sentences. I can 
at least say that I have never found m)-self mistaken 
in my judgment. I have observed that every 
writer whose sentences had to be completely re- 
written would also have required an entirely new 
brain before he was fit for anything. 

But how is it possible in a dead language to use 
correct constructions when there are so many pos- 
sible ways of arranging words ? Our language is 
so simple and uniform that 1 venture to say it will 
be easier to write and speak French correctly, if 
it were to die, than it is possible to write Latin 
and Greek now. How many inversions do we use 
to-day in Latin and Greek which would not have 
been permitted in the days of Cicero and Demos- 
thenes and which the refined ears of those orators 
would have rejected ? 

But, people will tell me, have we not in our 
language adjectives which are only used before a 
substantive, and others which are only used after ? 
How can our posterity learn these fine distinctions ? 
Reading good authors is not enough. I agree with 
you ; and if the French language dies, future savants, 
who care enough for our literature to learn and write 
our language, will be sure to write indifferently 
blanc bonnet or bonnet blanc, mechant auteur or auteur 



LETTER ON THE DEAF AND DUMB 177 

nic chant, homme galant and galant homme, and a vast 
number of similar phrases which would make non- 
sense of their writings were we to rise up to read 
them, but which would not prevent their ignorant 
contemporaries from exclaiming when they read some 
such piece : " Racine did not write more correctly," 
or " That is just like Despreaux ; Bossuet could not 
have said it better ; this prose has the music, the 
force, the elegance and ease of V^oltaire's." But if 
a limited number of difiiculties may cause those who 
come after us to stumble, what are we to think of 
our modern Greek and Latin authors and of the 
admiration they obtain? 

In talking to a deaf-mute it is found to be almost 
impossible to describe to him indefinite portions of 
quantity, number, space, or time, or to make him 
grasp any abstract idea. One can never be sure that 
he realises the difference in tense between / made, 
I have niade^ I was making, and / should have made. 
It is the same with conditional propositions. If, 
then, I was right in saying that at the origin of 
language men first named the principal objects of 
sense, such as fruit, water, trees, animals, serpents, 
etc. , and then named passions, places, and persons, 
qualities, seasons, etc., I may add that signs for' 
periods of time and tenses were invented last of all, i 
I imagine that for long centuries men had no other 
ten.ses than the present indicative and the infinitive, 
which became, according U) the circumstances, 
either a future or a [jast. 

I am supported in this conjecture by the present 

\2 



178 DIDEROT'S PHILOSOPHICAL WORKS 

state of the lingua franca — the language spoken by 
the various Christian nations trading with Turkey 
and the Levant ports. I believe it is the same to- 
day that it has always been, and that it will never 
develop. Its base is a corrupt Italian. The present 
infinitive is used for every tense, and its meaning is 
modified by guessing and by the other words of the 
sentence. Thus, / love thee, I was loving thee, I 
shall love thee, are all in lingua franca, ' * mi aniarti. " 
All have sung, Let each one sing, All will sing, are 
' ' tutti cantara. " I wisJi, I was wishing, I have 
wished, I should like to marry you, are " w/ voter i 
sposarti. " 

I imagine that inversions have crept into a 
language and been preserved in it because gesture 
language gave rise to the language of oratory, and 
that they naturally retained the position thus as- 
signed to them in the sentence. I also think that, 
for the same reason, as tense was not accurately 
defined even after conjunctions were formed, some 
languages, like Hebrew, which has no present or 
imperfect, did without certain tenses. They said 
Credidi propter quod locutus sum instead of Credo et 
ideo loquor : I have believed, and therefore L have 
spoken, instead of / believe, and therefore I speak. 

In other languages the same tense had two 
different meanings, as in the Greek language, where 
the aorist is at one time expressive of the present, 
at another of the past. Let me quote as an illustra- 
tion — theje are many others — a passage in the 
EncJiii-idion, which is perhaps not so familiar to you 



LETTER ON THE DEAF AND DUMB 179 

as some. Epictetus says : OeXova-i Kat avro] (piXo- 
crocfteiif. ' AvOpwire, TrpwTOv evrtcr/cei/^at, ottoiov €<tti to 
TTpay/ma ' elra Kut ttjv creauTou (f>v(jiv KUTafxaOe, ei Suvaaai 
j^acTTacrai. TlevTa&Xo^ eivat ^ouXei, J; TraAatcrT)/? ; 'iSe 
(reavTOu TOf? ppaxiovwi, tou^ juijpov^, Tr]v o(T(j>vv kutu- 
fxaOe (ch. xxix). A close translation is: "These 
men also wish to be philosophers ; O man, first /lave 
learnt what it is that you wish to be, Jiave studied 
your strength and the burden, have considered your 
arms and thighs, have tried your loins if you intend 
to be a pentathlete or a wrestler." This can be 
much better translated by substituting the present 
for the first and second aorists ; thus : " These men 
also wish to be philosophers. Man, first learn what 
it is you wish to be ; study your strength, and the 
burden ; consider your arms and thighs ; try your 
loins if you intend to be a pentathlete or a wrestler." 
The pentathlete, as you know, was one who intended 
to enter for all the gymnastic exercises. 

I consider these eccentricities of tense as the 
result of the original imperfection of languages 
and the traces of their original rudimentary state, 
against which common sense (which does not allow 
one and the same expression to render different 
ideas) vainly strove in after times. It was in vain ; 
the usage was fixed, and use won a victory over 
common sense. But there was, perhaps, not a single 
Latin and Greek author who was aware of this 
defect. I go further, and maintain tliat every 
Greek and Latin author pK^bably imagined in their 
speeches and writings tliat their words exactly 



i8o DIDEROT S PHILOSOPHICAL WORKS 

followed the order of their ideas. But evidently it 
was not so. When Cicero begins his oration pro 
Marcello by Diutunii silentii, Patres conscripti, quo 
eram his teinporibus usus, etc. , we can see that he 
was thinking of something before his " long silence " 
— an idea which was to follow and break in upon 
his "long silence," and which caused him to say 
Diuturni silentii instead of Diuturnum silentium. 
This remark upon the inversion of the beginning of 
this oration applies equally to all cases of inversion ; 
as a rule, in all Greek and Latin periods, however 
long they may be, we observe at once that the 
writer had some reason for preferring to use certain 
cases, and that there was not the same inversion in 
his ideas as in the order of his words. In the above 
sentence of Cicero's, what made him use the genitive 
case in Diuturni silentii^ the ablative in quo, the 
imperfect tense in eram, and so on, was the order 
of ideas pre-existing in his mind which did not 
coincide with the order of the words — an order he 
obeyed unconsciously, from a long practice in trans- 
position. Why should Cicero not have used in- 
version unconsciously, since we, who think our 
language follows the^natura.! order of ideas, do so 
too ? I was therefore justified in distinguishing 
between the natural and the acquired or scientific 
order of ideas and signs. 

You thought, sir, it might be argued, that there 
was no inversion in that period of Cicero's ; you are 
mistaken, but two considerations which have escaped 
your notice will convince you. The first is, that as 



LETTER ON THE DEAF AND DUMB i8i 

inversion proper, or the acquired, scientific and gram- 
matical order, is really an order in words which does 
not correspond to the order in ideas, what is inver- 
sion for one is not so for another, for different minds 
may put their words in different order. For in- 
stance, in the sentence serpenteni fuge I would ask 
you which is the principal idea. You may say that 
it is the serpent, but another will say it is flight ; 
and both of you may be right. A timid man thinks 
only of the serpent ; but the man who fears my 
danger more than he fears the serpent thinks only 
of my flight : one is overwhelmed by terror, the 
other gives me warning. The second thing I would 
remark is, that when we are presenting a series of 
ideas to others, and the main idea we wish to im- 
press upon them is not the one by which we our- 
selves are most impressed (because we and our 
hearers are differently situated), it is this former 
idea which we should present first, and such an in- 
version is but a matter of oratory. Let us apply 
these observations to the first period of the oration 
1>ro Marcello. I picture to myself Cicero mounting 
the tribune to speak to the people ; and I see that 
the first idea that will strike his audience is that it is 
a long time since he spoke to them ; hence diiiturtii 
silentii, his prolonged silence, is the first idea he must 
present to them, although the principal idea in his 
mind is rather hodiernus dies fineni attiilit ; for the 
orator's main preoccupation is the speech he is about 
to make, not his past silence. 1 notice another reason 
for the use of the genitive case in diuturni silentii \ 



i82 DIDEROTS PHILOSOPHICAL WORKS 

the audience could not realise the fact of Cicero's 
prolonged silence without seeking for the cause of 
it, and why he was at last breaking it. Now the 
genitive, being a case incomplete in itself, induces 
the minds of his hearers to travel onwards to meet 
the ideas that the orator could not present at once. 

These are, sir, the remarks upon the passage in 
question which you might have made. I am sure 
Cicero would have arranged this period quite 
differently, if, instead of speaking at Rome, he had 
been suddenly transported to Africa to plead at 
Carthage. This will show that what was not an 
inversion for Cicero's hearers would be and must 
be one for the orator himself. 

But to go a little further : I hold that when a 
phrase only contains very few ideas, it is very diffi- 
cult to determine the natural order of these ideas in 
relation to the speaker ; for if they are not all pre- 
sented at once, their succession is so rapid that it 
is often impossible to decide which strikes us first. 
Who can say if the mind cannot embrace a certain 
number at one and the same instant ? Perhaps you 
will call this paradoxical ; but let us examine to- 
gether how the article Jiic, ille, le came to be intro- 
duced into Latin and into our language. It will 
not be a long or difficult matter, and may induce 
you to accept a position that you find distasteful 
at present. 

Let us first transport ourselves to the period when 
Latin adjectives and substantives which denoted the 
qualities perceived by sense in various natural objects 



LETTER ON THE DEAF AND DUMB 183 

were almost all invented, but when no expression 
had yet been found for those intellectual subtilties 
which philosophy has even to-day much difficulty in 
distinguishing. Next imagine two hungry men, one 
of whom could see no food, while the other stood 
beneath a tree so very tall that he could not reach 
its fruit. Their sensations make both these men 
speak ; the first would say : / am hungry, I would 
like to eat ; and the second, What beautiful fruit / 
I am hungry, I would like to eat. Now, it is obvious 
that the former has adequately expressed in words 
all that passed in his mind ; while the latter Jias left 
something unexpressed — a portion of his thought 
must be supplied. The expression / would like to 
eat, when no food is to be seen, applies generally to 
all food that could appease hunger ; but the same 
expression is limited in its application, and refers 
only to a fine fruit when that fruit is to be seen. 
Thus, though they both said / am hungry, I ivould 
like to eat, the man who exclaimed "What a fine 
fruit ! " returned in thought to this fruit, and 1 make 
no doubt that if the article le had been in use he 
would have said: What fijie fruit ! lam hungry ; 
I would like to eat this (or this I would like to eat). 
The article le or cclui in this case and in other similar 
cases denotes that the mind reverts to an object 
which it had previously considered, and the inven- 
tion of this symbol is, I think, a proof of the 
progress of the mind. 

Do not raise difficulties about the position this 
word ought to occupy in the sentence in accordance 



i84 DIDEROTS PHILOSOPHICAL WORKS 

with the natural order of ideas, for though these 
statements, WJiat fine fruit ! I am hiuigry , I would 
like to eat that, are each expressed by two or three 
words, each only denotes a single notion ; the mid- 
most sentence, / am hung}']', is expressed in Latin 
by a single word esurio. The fruit and its quality 
are perceived at the same time ; and when a Roman 
said esurio he only imagined he was expressing a 
single idea. / would much like to eat that are only 
modes of single sensation. / denotes the person 
who experiences it ; would like to eat, the desire and 
the natnire of the sensation experienced ; much, its 
intensity ; it, the presence of the desired object. But 
in the mind there is not the successive development 
we observe in speech ; if it had twenty mouths, and 
each mouth able to say a word, all the above ideas 
would be expressed at once. This could be ex- 
cellently executed on Father Castel's harpsichord, 
if our dumb friend's theory were in practice and 
each colour combined to form words. No tongue 
would approach it in the rapidity of its speech. 
But as we have not many mouths, people have 
attached several ideas to a single term. If there 
were more of these vigorous terms, instead of the 
tongue panting after the mind, such a number of 
ideas could be expressed at once that the mind 
would lag after the tongue which hastened in advance 
of it. What would then be the fate of inversion, 
which implies a disintegration of many simultaneous 
mental impressions and a number of words ? Al- 
though we have few words equivalent to a long 



LETTER ON THE DEAF AND DUMB 185 

speech, we have some, and Greek and Latin are 
full of them ; they are at once understood when 
used, and this is a proof that the mind experiences 
a multitude of sensations, if not simultaneously, 
yet in such rapid succession that it is impossible 
to distinguish their order. 

If I had to explain this system of the human 
understanding to one who found it difficult to grasp 
abstract ideas, I should say, "Consider man as a 
walking clock ; the heart as its mainspring, the 
contents of the thorax as the principal parts of the 
works ; look on the head as a bell furnished with 
little hammers attached to an infinite number of 
threads which are carried to all corners of the clock- 
case. Fix upon the bell one of those little figures 
with which we ornament the top of our clocks, and 
let it listen, like a musician who listens to see if his 
instrument is in tune : this little figure is the soul. 
If many of these little threads are pulled at once, 
the bell will be struck several times, and the little 
figurewill hear several notessimultaneously. Imagine 
that there are some of these threads that are always 
being pulled ; and just as we only notice the noise 
of Paris by day when it ceases at night, we shall be 
unconscious of some sensations which are continuous, 
such as of our existence. The mind, especially in 
health, is unconscious of its own existence, unless 
it deliberately examines itself. When we are well, 
we are unconscious of any part of our body ; and if 
any part draws attention to itself by pain, we are 
certainly not well ; and if it is by a pleasurable 



1 86 DIDEROT S PHILOSOPHICAL WORKS 

sensation, it is by no means certain that we are 
the better for it." 

I could pursue my analogy still further, and add 
that the sounds produced by the bell do not die 
away at once, but have some duration ; that they 
produce chords with the sounds that follow, and 
the little figure that listens compares them, and 
pronounces them harmonious or dissonant ; that 
memory, which we need to form opinions and to 
speak, is the resonance of the bell ; the judgment, 
the formation of chords ; and speech, a succession 
of chords. It is not without reason that some brains 
are said to be "cracked," like a bell. And is not 
the law, which is so necessary in a series of harmonies, 
of having at least one note common to the chord 
and that following it, also applicable ? Does not 
this common note resemble the middle term of a 
syllogism ? And what else is the likeness we observe 
in certain minds but the result of some freak of 
nature by which two intervals are marked, one a 
fifth and the other a third, in relation to another 
note ? By this fertile analogy, and with all the 
madness of Pythagoras, I might demonstrate the 
wisdom of that Scythian law which prescribed one 
friend as a necessity, permitted two, and forbade 
three. Among the Scythians, I might say, a man 
was "out of tune" if the note which he gave forth 
found no harmonic among his fellow-men ; three 
friends would make a perfect accord ; while a fourth 
superadded would be but a repetition of one of the 
former three, or would introduce a discordant note. 



LETTER ON THE DEAF AND DUMB 187 

But enough of this language of metaphor, which 
at best is but fitted to amuse and arrest the volatile 
mind of a child ; let us come back to philosophy, 
which requires arguments and not analogies. 

When people examined the various utterances 
called forth by the sensations of hunger and thirst, 
they observed that the same terms were used to 
express different notions ; and the symbols j^z^, he, 
vie, the, and many others, were invented for the sake 
of precision. A mental state during an indivisible 
moment of time was expressed by a number of words 
which divided the complete expression into a number 
of parts ; and because these words were uttered one 
after another, and were only understood in the order 
they were spoken, it was thought that the sensations 
they expressed were experienced by the mind in the 
same order. But this is not the case. Our mental 
state is one thing, our analysis of it quite another. 
This is so, whether we analyse it to ourselves or to 
others. The complete and instantaneous perception 
of this state is one thing ; the detailed and continuous 
effort of attention we make to analyse it, state it, 
and explain it to others, another. Our mind is a 
moving scene, which we are perpetually copying. 
We spend a great deal of time in rendering it faith- 
fully ; but the original exists as a complete whole,/ 
for the mind does not proceed step by step, like! 
expression. The brush takes time to represent! 
what the artist's eye sees in an instant. In the 
growth of language, decomposition was a necessity ; 
but to sec an object, to admire it, to experience an 



1 88 DIDEROT S PHILOSOPHICAL WORKS 

agreeable sensation, and to desire to possess it, is 
but an instantaneous emotion, rendered in Greek 
and Latin by a single word. This word once uttered, 
all is said and understood. Ah, how our understand- 
ing is modified by words, and how cold a copy of 
reality is the most vigorous utterance ! 

Les ronces degouttantes 
Portent de ses cheveux les depouilles sanglantes?- 

This is one of the most life-like pictures I know, 
but yet how far is it from my imagination ! 

I beg of you, sir, to consider these points if you 
wish for a juster notion of this complex question 
of inversion. For my part, I am fitter to gather a 
cloud than to scatter it, to suspend my judgment 
than to give a verdict ; and I am going to prove 
that if the paradox that I have just advanced does 
not hold good, and if our mind does not allow of 
several perceptions at one and the same time, it 
would be impossible to think and speak ; for 
thought and speech consist in the comparison of 
two or more ideas. Now, how is it possible to 
compare ideas which are not both at once present in 
the mind ? You allow that we can experience more 
than one sensation at a time ; for example, we can 
perceive the colour and shape of a body at the same 
time ; why not also abstract ideas ? Does not 
memory employ two ideas present at the same time 
in the mind — the actual idea, and the remembrance 
of the former ? For my part, I think that is why a 
good judgment and a good memory are rarely found 

^ Racine, Fhcdre, Acte v, Scene vi. 



LETTER ON THE DEAF AND DUMB 189 

together. A good memory presupposes a great 
facility in embracing various ideas at one and the 
same moment or in rapid succession ; and this gift 
interferes with the tranquil examination ot a small 
number of ideas which the mind ought to contem- 
plate with fixed attention. A mind stored with a 
huge variety of things is like a library of odd 
volumes ; it is like one of these German compila- 
tions bristling with Hebrew, Arabic, Greek, or 
Latin quotations put together without judgment or 
taste ; which are ponderous as it is, and which will 
grow more and more ponderous, and grow none the 
better ; a store full of analyses and appreciations and 
ill-digested works, and shops of mixed goods where 
the memorandum alone is in order ; a commentary 
where we scarcely ever find what we want, but 
often what we don't want, and almost always what 
we want is lost in a heap of rubbish. 

It follows from the foregoing statements there 
is not, and perhaps there cannot be, inversion in the 
mind, especially if the object contemplated be an 
abstract one ; and though a Greek may say : viKijcrai 
oXv/nTTia deXei^', /cayco, vt] toi/? Oeov^' ko/jl'^ov yci/o 
ecTTiu (Epictetus, Enc/nn'dion, ch. xxix) and a 
Roman Honores plurwiuni valent apud prudentes, si 
sibi collatos intelligani^ French syntax and common 
sense find this Greek and Latin syntax embarrassing, 
and say without an)- inversion : You ivould like 
to belong to the French Academy ? So should I ; 
for it is an honourable distinction, and the wise man 
may value a distinction which lie feels he deserves. 



190 DIDEROT S PHILOSOPHICAL WORKS 

I would not therefore care to maintain without 
distinction the general statement that the Romans 
did not use inversion, whereas we do. I should 
merely say, if instead of comparing our sentence 
with the order of ideas we compared it with the 
order of the inversion of words, with gesture- 
language, for which spoken language has been 
gradually substituted, it would appear that we 
invert ; and we use more inversions than any other 
nation in the world. But if our construction is com.- 
pared with that of a mind influenced by Greek and 
Latin syntax, we have the fewest possible inversions. 
We express things in French in the order the mind 
has to consider them, whatever the language. 
Cicero, if we may say so, followed the French 
order before obeying the Latin, 
i/ It follows that, since the communication of 
thought is the principal object of a language, 
French is of all languages the best organised, the 
most precise, and the most excellent, for it retains 
less than any other the negligences, or what I may 
call the lispings, of the childhood of the race : in 
other words, by having no inversions we have gained 
in clearness and precision, which are essential 
qualities in writing ; but on the other hand we have 
lost in warmth, in energy, and in eloquence. I may 
add that the orderly and didactic movement of our 
language makes it peculiarly suitable for science ; but 
the Latin, Italian, and English languages, which 
allow of inversion, are more suited for literature. 
We can express the intellect better than any other 



LETTER ON THE DEAF AND DUMB 191 

nation, and common sense will choose French for 
its utterances ; but imagination and the passions 
will prefer the ancient tongues, and that of our 
neighbours, to ours. French should be the language 
of society and of the schools of philosophy ; Greek, 
Latin, and English, the language of our lecture- 
halls, pulpits, and theatres ; but if truth return to 
earth, I believe French would be her chosen speech, 
while Greek, Latin and the other tongues will be 
the language of fables and falsehoods. French is 
the language for teaching, enlightening, and con- 
vincing ; Greek, Latin, Italian and English for 
persuading, stirring the passions, and hoodwinking ; 
talk Greek or Latin or Italian to the multitude, but 
talk French to the wise. 

Another drawback to languages with inversions 
is that the attention ol the reader or hearer is 
taxed. How many cases, tenses, and termina- 
tions are there not to bear in mind in a long 
Greek or Latin sentence ? It is almost incomprehen- 
sible until one reaches the last word ; while in French 
there is none of this strain, and we can understand 
as we go along. Ideas in our language are presented 
in the order they presented themselves to the mind, 
whether the mind be Greek or Latin. La Bruyere 
is less fatiguing to read in the long run than Livy, 
though the former is a profound moralist, the latter 
a simple historian ; but the historian sets his 
sentences and phrases so artificially, that we are 
continually removing them frcnn their sockets, and 
restoring them to their clear and natural order, 



192 DIDEROTS PHILOSOPHICAL WORKS 

and insensibly weary of the toil, just as the strongest 
arm wearies of a small weight which is constantly 
carried. So, take it all in all, our pedestrian 
language has the advantage of utility over the 
others. 

But there is a motive which both in French and 
in the ancient tongues disturbs the natural order of 
ideas, and that is the desire for harmony of style — a 
desire which is now become so imperative that we 
are ready to sacrifice a great deal to it. For we 
must distinguish between three phases that all 
languages pass through when they have left that 
earliest stage when they were merely a confusion of 
cries and gestures which we may call the animal 
phase. These three phases are birth, development, 
and perfection. The newly-born language was 
made up of words and gestures in which adjectives 
without gender or case and verbs without tenses and 
not governing cases preserved the same terminations 
throughout. In the developed language there were 
words, cases, genders ; and verbs were conjugated 
and governed cases. In fact, there were all the 
necessary signs for expressing thought, but nothing 
more. In the perfected language, beauty was 
required ; for people thought the ear must be 
pleased as well as the mind. But as the subsidiary 
is often thus set before the principal thing in the 
sentence, the order of ideas is often disturbed to 
procure this harmony»of style. This is what Cicero 
has done in part of his opening period in the pro 
Marcello ; for the first idea that he should have 



LETTER ON THE DEAF AND DUMB 193 

presented to his hearers, after that of his long 
silence, was the reason for this silence. He should 
therefore have said : Dliitiirni silentii, qtio, non 
tiniore aliquo, sed partiin dolore, partim verecundia, 
erani his temporibus usus, Jinein, hodiernus dies 
attulit. Compare this sentence with the original, and 
you will find no reason why it should not have been 
used by him, except that of harmony. Another 
instance is the great orator's phrase, Alois terrorque 
civium ac sociorum Ronianonini,^ where it is evident 
that the natural order required terror viorsque. 
There are a number of other examples 1 could quote. 
This leads us to the question whether the natural 
order should be sacrificed for the sake of harnion)'. 
1 think this is permissible when the inverted ideas 
are so close to one another that they strike the ear 
and mind almost at the same moment ; just as we 
transpose the fundamental bass into a higher clef 
to make it more tuneful, although the transposed 
bass will only be agreeable so long as the ear can 
distinguish the natural progressions of the funda- 
mental bass which suggested it. Do not think from 
this remark that I am a great musician ; it is only 
two days ago that I began to be one ; but you know 
how one likes to parade some new accomplishment. 
I think we might discover several analogies between 
musical harmony and harmony of style. When, for 
instance, we are about to describe some great or 
wonderful events, the harmony of style must be 
sacrificed or at least disturbed. So we say : 

' " The death and panic of the Roman citizens and their allies." 



/< 



194 DIDEROT'S PHILOSOPHICAL WORKS 

Magnum Jovis incrementum.^ 

Nee brachia longo 
Margine ierrarum porrexerat Amphitrite? 
Ferte ciii ferrum, date tela, scandite muros.'^ 

Vita quoque omnis 
Oinnibus e nervis atque ossibus exsolvalur.^ 
Longo sed proximus intervalio.^ 

In a similar manner in music we must sometimes 
I shock the ear in order to surprise and please the 
imagination. We may also observe, that though 
these licences in the order of words are only per- 
mitted for the sake of the harmony of style, licences 
in harmony, on the other hand, are chiefly taken to 
arouse and give rise in the most natural order to 
the ideas which the musician wishes to express. 
^ In speech we must distinguish between thought 
and expression ; if thought is expressed with purity, 
clarity, and precision, this is quite sufficient for 
> ordinary conversation ; if you add to these a certain 
distinction in the use of words and a certain rhythm 
and harmony, you will have a style well fitted for 
an orator, but you will still be far removed from 
poetry, especially from the grand style of the epic 
and the ode. There is a spirit in the poet's lan- 
guage which moves there and breathes life into each 
syllable. What is this spirit ? I have felt its pres- 
ence, but find it difficult to describe, 1 may say 
that it states and paints objects at the same time ; 

1 Virgil, Bucol., Eclog. iv, v. 49. 

^ Ovid, Metam., lib. i, vv. 13-14. 

■* Virgil, ^-Eneid, lib. ix, v. 37. 

^ Lucretius, De rertiin nat., lib. i, vv. S10-811. 

^ Virgil, .-iLncid, lib. v, v, 320. 



LETTER ON THE DEAF AND DUMB 195 

it appeals not only to the understanding, but to the 
soul which it stirs and the imagination that sees 
and the ear that hears. The lines are not merely 
a chain of vigorous words which express the thought 
both forcibly and nobly, but a series of hieroglyphs, 
one after another, which picture the thought to us 
vividly. I might say that all poetry is symbolic. 

But it is not everyone who can understand these 
symbols. In order to feel their full force we must 
be, as it were, in the creative mood. The poet says : 

Et des fieuves frarigaises les eaux cnsanglantees 
Ne portaient que des morts aux mers epoitvantees} 

Does everybody appreciate the value of the first 
syllable of the word portaient, which paints us the 
waters swollen with corpses and the stream choked, 
as it were, by this obstacle ? And in the second 
syllable of the word, does everyone see the mass of 
waters and dead bodies subsiding and moving out 
to sea ? The terror of the sea is brought before us 
all in the word cpouvantces, but the stress laid on 
the third syllable brings before me the vast extent 
of the ocean. Again, the poet says : 

y .' y ' ^ / / ''. / ■ '' 

Soupire, etend les bras, ferme Vocil et s^endort? 

All exclaim, ' ' How fine ! " but it is not by counting 
the syllables on one's fingers that we can judge how 
fortunate the poet was, when expressing a sigh, to 
have such a word as soupire with its long-drawn 
sound. We read ctend les bras, but -vve hardly realise 

' Voltaire, Ilenriade, chant ii, v. 357, 
- Uuileau, Lutriii, chant ii, v. 164. 



196 DIDEROT S PHILOSOPHICAL WORKS 

how the impression of length and lassitude is ex- 
pressed by the long monosyllable bras, and the 
' ' outstretched arms " fall so reposefuUy on the ear 
at the close of the first hemistich of the line. Do we 
notice the rapid movement of the eyelid in ferine 
I'ceil and the almost imperceptible change from 
wakefulness to sleep at the ^close of the second 
hemistich ferine I ail ct s'endort ? 

The cultivated reader will of course observe that 
the poet has four actions to represent, and that his 
line is divided into four parts ; that the two last 
actions are closely interrelated, and that they have 
scarcely an interval between them ; and that the two 
last and corresponding parts of the line are also 
closely linked, united as they are by the rapidity 
of the movement of the penultimate part and by a 
conjunction ; that each of the actions takes only its 
proper proportion of time in the verse ; and that as 
all four actions are comprised in this small space, 
the poet has expressed their rapid succession in 
nature. That is the kind of problem that the poet's 
genius solves unconsciously ; but do his readers 
realise his skill? Certainly not; and I shall not 
therefore be surprised if those readers of Boileau 
(and there are many) who have not understood the 
meaning of his symbols laugh at my commentary, 
and, remembering the CJief-d'ceiivrc d'un inconnu,^ 
treat me as a visionary. 



^ Le chcf-(£ auvre d'un iiuoniiu, avcc des remarques savantes, par 
M. le docteur Chrysostome iVlathanasius, La Haye, 1 7 14. This liitle 
hu cfesprit was the work of Themiseul de Saint Ilyacinthe, S'Grave- 



LETTER ON THE DEAF AND DUMB 197 

I used to think, like everybody else, that one poet 

could translate another, but I have found out my 

mistake. The thought can be rendered, and perhaps 

by good fortune the equivalent expression. Homer 

said : eKkay^av S' ap oia-rol {Iliad, Cant, i, v. 46) 

and tela sonatit Jmmeris is Virgil's version {u^Eneid, 

lib. iv, V. 149). That is something, but not all ; 

the suggestive s}'mbolism, the subtle hieroglyphs 

which pervade a long description, and which depend 

on the distribution of long and short syllables in an 

unaccented language and on the distribution of vowels 

between consonants in all languages, disappear even 

in the best translation. 

Virgil writes of Euryalus stricken by a mortal 

wound : 

Pulchrosque per arius 
It cruor, inque humcros cervix collapsa reaimbit : 
Purpuretis veluti qiium flos, succisus aratro, 
Latiguescit moriens ; lassove papavera collo 
Demisere caput, pluviam qmo/i forte gravantur.^ 

I should just as soon expect these lines to have 
sprung from letters scattered at haphazard, as that 

sand, Sallengre, Prosper iMarchand, and others, who wrote admiring 
Comments in all languages upon the words of a song beginning : 
" L'autre jour Colin nialade 
Dedans son lit 
D'une grosse maladie 
Pensant moiirir.'' 
The authors were ridiculing German scholarship. — (A) 
' ^Eiieid, lili. ix, vv. 433-437 : 

Hlood trickles o'er his limbs of snow, 
His head sinks gradually low ; 
Thus severed by the ruthless plough, 

Dim fades a pur|)le fluwer : 
Their weary necks so poppies bow 
O'erladen by the shower. 

{Trs. Conington.) 



yf 



198 DIDEROT'S PHILOSOPHICAL WORKS 

a translation could render all the suggestive beauties : 
the gush of blood, it cruor ; the drooping head of the 
dying lad, cervix collapsa recumbit ; the sound of 
the scythe,^ succisus ; the languor of death, languescit 
vioriens ; the softness of the poppystalk, lassove 
papavera collo ; and the demisere caput and gravantur 
suitably complete the picture. Demisere is as soft 
as the stalk of a flower ; gravantur is as heavy as 
its cup heavy with rain ; collapsa expresses effort 
and relapse. The same symbolic suggestion is to be 
found in papavera ; the first two syllables show the 
poppy with head erect, and in the last two it droops. 
All these pictures are compressed in these four lines 
of Virgil. You have been affected by the happy 
parody in Petronius ^ of Virgil's lassove papavera collo 
applied to the exhaustion of Ascyltus when he quits 
Circe ; and you would not have so keenly appreciated 
Petronius' use of the phrase if you did not recognise 
in it a faithful picture of the plight of Ascyltus. 

This analysis of Virgil ought to be enough for 
me ; and after drawing attention to more beauties 
than are perhaps to be found in the original — 
certainly more than the poet deliberately thought 
of, — my imagination and taste ought to be completely 
satisfied. No, sir ; I am about to expose myself to 
two criticisms — of having seen beauties that were 

^ Aratrum does not mean a scythe, but the reason for this rendering 
will appear a little further on. — (D) 

Ilia solo fixos oculos aversa tenebat 

Nee prius incepto vultum sermone movetur 

Quam lentje salices, lassove papavera collo. 

Satyricon. — (Br) 



LETTER ON THE DEAF AND DUMB 199 

not there, and criticised defects that were also non- 
existent. Now for it. I think the word gravantur 
is a Httle too heavy for the Hght poppy flower, and 
the aratro following succisus does not to me complete 
the suggestive picture. I am convinced Homer 
would have concluded his line with a word that 
would have continued the sound of a cutting imple- 
ment, or have depicted to my imagination the soft 
drooping of a flower. ^ 

It is the recognition of, or rather the vivid feeling I 
for these symbolic expressions which are lost on the 
ordinary reader, that discourages men of genius from 
attempting a translation. That is why Virgil said 
that it is as difficult to take a line from Homer as 
to snatch a nail from the club of Hercules. The 
more a poet uses this symbolism, the more difficult 
he is to translate, and Homer is full of such suggestive 
symbols. Let me quote those lines where Jupiter 
with his dark brows confirms to ivory-shouldered 
Thetis his promise to avenge the injustice done to 
her son : 

H, Kttt Kvavir\(T\v Itv (xfifivcri I'tvrrc Kpnvnov • 
Afifipoariai K apa ^airat eTrep/xorrai'To di'aKTO? 
Kparos ttTr' dOavdroio ' fj.eyav 8' iXtXi^ev OAd/xttoi'. 

I/i'ad, i, 528-530.^ 

How many images there arc in these three lines ! 

We see Jupiter's frown in ftt' otppum, in vevrre Kpovum'^ 

and especially in the happy repetition of the letter 

k in //, Koi Kvav€r}(Tiv\ his flowing locks are expressed 

in eTrepfjwcravTO ai^a/fro? ; the immortal head of the 

* "He spake and nodded with his dark-hued brows ; and the ambrosial 
locks fronn his immortal head shook ; and great Olympus trembled." 



200 DIDEROT S PHILOSOPHICAL WORKS 

god is majestically lifted by the elision oi airo in 
Kparog air adavdroio ; the shaking of Olympus is 
expressed in the two first syllables of eXeXi^ev ; the 
size and sound of Olympus in the last syllables of 
fxeyav and eXeXi^ev and in the last word where a// 
Oly7npus trembles with its close. 

The line which I have just written is the feeble 
rendering of two symbols — one from Virgil, the other 
from Homer ; one of shock, the other of fall : 

And all Olympus trembles with its close. 

Procumbit humi bos.^ 

It is the repetition of the letter / in eXeXi^ev 
OXviuiroi' which gives the idea of trembling and 
shock. The same repetition of I's is found in my 
" Olympus trembles " ; but as the I's are not so close 
together as in iXeXi^ev" OXv/ulttov, the shaking is less 
rapid and also less like the movement of frowning 
brows. " Trembles with its close" represents /r^- 
cHinbit Jmnii bos fairly well, though the last word 
of my line is less heavy and emphatic than bos, 
which is a greater contrast with the word ]inmi than 
close is with the short words immediately preceding 
it. Virgil's monosyllable is thus more isolated than 
mine, and the fall of his ox heavier and more com- 
plete than the close of my line. 

An observation I may make here, which io just as 
apposite as the speech of the Emperor of Mexico in 
the chapter about coaches in Montaigne, ^ is that 
people had a singular veneration for the ancients, 

^ ^'?lueid lib. V, v. 481. ^ Essais, liv. iii, ch. vi. 



LETTER ON THE DEAF AND DUMB 201 

and a great tear of Boileau, when they asked him 
if the three following hnes of Homer, 

Zei' Trdrep, aXXa <tv pvcrai vtt lyepos via<; A^j^atojv * 
IToi't^ctov 8' aWprjv, Sos o' o(f)0a\fjio7.aLV iSiaOai • 
'Ev 8e cfxieL kol oXeacroy, CTret vu tol euaoev ovtox;. 

{Iliad, Cant, xvii, v. 645.) 

were to be interpreted as Longinus ^ had inter- 
preted them, and as Boileau and La Motte had 
translated them, or not. 

These are the true feelings of a warrior, cry 
Boileau ^ and the orator Longinus. He does not 
ask for his life to be spared, for a hero is above 
such a weakness ; but as he sees no opportunity of 
showing his courage in the midst of darkness, he is 
provoked at not fighting ; he therefore is anxious to 
ask for daylight, so that his end may at least be 
worthy of him, even if he has to fight with Jupiter 
himself. 

Well, sir, I shall answer Longinus and Boileau : it 
is not a question here of the feelings of a warrior, 
nor what he would say in the circumstances in 
which Ajax is placed (Homer apparently knew these 
things as well as you), but of translating these lines 
of Homer correctly. And if it turns out that there 
are none of these sentiments }ou praise in these 
lines, what becomes of your praises and reflections ? 
What must we think of Longinus, La Motte, and 
Boileau, if we find they have invented and inserted 

' Treatise on the Sitblinie, section ix. 

- Grand Dieu ! chassc la nuit (|ui nous coiivre les yeux 

Et combats Cf)ntre nous a la clarte ties cieux. 

Boileau, translating the '/'realise on the Sublime, ch. vii. 



202 DIDEROT S PHILOSOPHICAL WORKS 

impious boasting in the place of a sublime and 
touching prayer ? Now, this is just what has hap- 
pened. Read these three lines of Homer as many 
times as you please, and you will find nothing but 
" Father of gods and men, drive away the dark- 
ness which covers our eyes, and, since you have 
resolved to slay us, let us die in the light." 

And must we thus without a struggle die ? 
Great God, drive off the darkness from our eyes, 
And let us perish under open skies. 

This translation does not give the pathos of 
Homer's lines, but at any rate it avoids the nonsense 
of La Motte and Boileau. 

There is no defiance of Jupiter here, nothing but 
a hero ready for death, if it be the will of Jupiter, 
and. asking no grace but to die fighting. Zeu irarep, 
Jupiter, Pater ! Is that how the philosopher Men- 
ippus addresses Jupiter ? 

At the present day, when we are no longer at the 
mercy of the lines of the redoubtable Boileau, and 
the philosophic spirit has taught us to see in things 
only what is actually there and to praise only what 
is truly beautiful, I appeal to the learned men and 
men of taste, to Monsieur de Voltaire, to Monsieur 
de Fontenelle, and others, and I ask them if Boileau 
and La Motte have not spoilt Homer's Ajax, and 
Longinus vainly attempted to add to Homer's 
beauties. I recognise the greatness of Longinus, 
Boileau, and La Motte ; but I am not attacking 
them, only defending Homer. 

This passage of Jupiter's oath and many others I 



LETTER ON THE DEAF AND DUMB 203 

could quote are sufficient evidence that it is useless 
to try to add to Homer's beauties ; and Ajax' 
speech is proof positive that in trying to add 
beauties to him there is a risk of destroying the 
genuine beauties of the original. However talented 
we are, we cannot write better than Homer, when 
he is at his best. At any rate, let us understand 
him before trying to outdo him. But he is so full 
of that poetic symbolism I was just now speaking 
of, that we cannot claim that we have completely 
understood him when we have only read him ten 
times. We might sa)' that Boileau in literature has 
suffered the same fate as Descartes in philosophy, 
and it is through them we ha\e learnt to correct 
their minor errors. y 

If you ask me when this hieroglyphic use of f 
syllables was introduced into a language, whether it . 
is a peculiarity of a language in its early stage or / 
in the formative period, or of the perfected period, 
I make answer that when men contrived their 
primitive language they were apparently only 
influenced by the facility or difficulty of pronounc- 
ing certain syllables, and this facility (or difficulty) 1 
was conditioned by the conformation of the organs 
of speech. They did not seem to have considered 
what relation the elements of these words might 
have from their quantity or sound to the physical 
characteristics of the objects they stood for. The 
vowel A, which is the easiest to pronounce, was first 
used, and it was modified in \arious wa)'s before 
another sound was employed. The Hebrew Ian- 



204 DIDEROT S PHILOSOPHICAL WORKS 

guage supports this conjecture ; most of its words 
are modifications of the vowel A, and this pecu- 
liarity is in harmony with the traditions of this 
people's antiquity. If we examine Hebrew closely, 
we shall incline to consider it the language of the 
primitive inhabitants of the earth. As for the 
Greeks, they must have had the use of speech for a 
long time and have thoroughly practised the subtilties 
of pronunciation before they introduced quantity, 
harmony, and syllabic imitation of noises and actions. 
On the analogy of children, who, when they wish to 
denote an object whose name is not known to them, 
substitute for the name some of the object's sensible 
peculiarities, 1 conjecture that it was during the tran- 
sition from the primitive stage to the formative that 
language became enriched with s}'llabic harmon}', 
and that rhythmic harmony was introduced into 
writings as the language passed from the formative 

yito the perfected stage. 

Whether these periods correspond to the actual 
development of language or no, one who has no 
feeling for the symbolic significance of words will 
often only appreciate the definite significance oi 
epithets, and will be apt to call them superfluous ; 
he w ill criticise ideas as loose, and images as far- 
fetched, because he is blind to their subtle relation 

Uo the subject ; he will not see that in Virgil's it 
cruor the word it resembles in sound a gush of 
blood and the falling of rain-drops on the leaves of 
a flower, and so he will lose one of the trifles which 
are all-important among the best writers. 



; 



LETTER ON THE DEAF AND DUMB 205 

Reading the most lucid poets, therefore, is not 
without its difficulties ; and I can assure you there 
are a thousand men who can understand a geome- 
trician for one who can understand a poet ; since 
there are a thousand men who have common sense 
for one man who has taste, and a thousand men of 
taste for one whose taste is exquisite. 

I am told that in the Abbe de Bernis' discourse 
when Monsieur de Bissy was received into the 
French Academy, Racine was blamed for want of 
taste in the passage where he speaks of Mippolytus: 

// suivait, tout pens if, le che/iii/i de Alyccnes ; 
Sa main sur les chevaux laissait Jlotter les renes ; 
Ses superbes coursiers, (/u'ott voyait autrefois 
Pleifts (Tune ardeur si noble obcir a sa voix, 
L'(jcil morne maintenunt et la tete baissee, 
Semblaient se conformer a sa triste pensee} 

If the Abbe is criticising the actual description, and 
not its suitability in the context, it would be diffi- 
cult to find a better and more modern instance of the 
difficulty I just now spoke of, of reading poets. 

There is nothing in these lines but speaks of 
depression and sorrow : 

// stiivait, tout pensif le chemin de Mycenes ; 
Sa main sur les chevaux laissait flatter les rates. 

Les chevaux is better than ses chevaux ; and how well 
the picture of what these superb horses once were 

' "All pensive, he followed the road to Mycenje; his hands loosed 
the reins on his horses' necks ; and his superb horses, Uiat used to obey 
his voice with a noble tire, now with bent head and lack-lustre eye 
seemed in sympathy with their master's sadness." — J'hedre, Acte v, 
Scene vi. 



2o6 DIDEROT S PHILOSOPHICAL WORKS 

contrasts with their present condition ! The nodding 
of a horse's head, as it jogs wearily along, is imitated 
in a certain syllabic nutation in the line itself : 

Vceil morne maintenani et la tcte baissee. 
But see how the poet brings all these details round 
to his hero : 

Ses superbes coursiers, etc. . . . 
Semblaient se conformtr a sa triste pensee. 

The word "seemed" seems too cautious for a poet, 
for it is wxll known that animals attached to man 
are affected by the signs of his joy or sorrow : the 
elephant is affected by the death of his driver, the 
dog mingles his voice with his master's, and the horse 
is affected if his driver is sad. Racine's description 
is therefore true to life : it is a noble description 
and a poetic picture which a painter might reproduce 
successfully. Poetry, painting, good taste, and truth 
are all united for Racine and against the Abbe de 
Bernis' critique.^ 

But if we were taught at Louis le Grand to notice 
all the beauties of this passage of Racine's tragedy, 
we were also told that they were out of place in the 
mouth of Theramene, and that Thesee would have 
had some excuse for stopping him and saying : 
' ' Enough of my son's chariot and horses ; tell me 

' [In an addendum to this Letter Diderot apologises for his criticism of 
the Abbe de Bernis. He was at first told by a friend, who was present 
at the meeting of the French Academy, that the Abbe de Bernis had 
criticised these lines of Racine's as both misplaced and bad in them- 
selves. He was afterwards informed that the Abbe merely criticised 
them as misplaced ; and, far from claiming this criticism as original, he 
quoted the lines as oae of the most familiar instances of such mis- 
placed eloquence.] 



LETTER ON THE DEAF AND DUMB 207 

about him." It was not thus, the celebrated Poree 
told us, that Antilochus announced the death of 
Patroclos to Achilles. Antilochus approaches the 
hero with tears in his eyes, and tells him the terrible 
news in a few words : " Patroclos is no more. They 
are fighting for his body. Hector has his armour." 
There is more of the sublime in these two lines of 
Homer than in all the pompous declamation of 
Racine. , ' ' Achilles, you have no longer a friend, 
and your armour is lost." At these words we all 
teel that Achilles must rush into the fray. When a 
passage sins against truth and propriety, it is not 
beautiful, either in tragedy or in epic. The details 
in Racine's lines would only be suitable in the mouth 
of a poet describing the death of one of his heroes. 

So our learned professor of rhetoric taught us. 
He possessed both taste and intelligence, and it 
might be said of him that he was the "last of the 
Greeks." But this Philopcemen fell into the same 
mistake as people make to-day : he filled his works 
too full of cleverness, and kept his taste for other 
people's works. 

To return to the Abbe de Bernis. Did he only 
wish to maintain that Racine's description was out 
of place ? That is exactly what Leather Poree taught 
us thirty or forty years ago. Or did he wish to hold 
up the passage I have quoted as an example of bad 
taste ? That is an original idea, but is it justified ? 

I am told that there arc many well-expressed and 
well-reasoned passages in the Abbe de Bernis' dis- 
course : you are more likely to know this than I, as 



208 DIDEROT S PHILOSOPHICAL WORKS 

you always take the opportunity of hearing such 
things. If it happens the Abbe de Bernis' discourse 
does not contain the offending passage I have just 
spoken of, and I have received an imperfect account 
of it, that will make another instance of the utility 
of a letter for the use of those who hear and 
speak. 
/ Wherever the language of signs is to be seen, 
whether in a line of poetry or on an obelisk,^ whether 
in a work of imagination or of mystery, it requires 
a high degree of imagination and penetration to 
understand it. But if it is so difficult to understand 
poetry, why is it not more difficult to write poetry ? 
I shall be told that "everyone writes poetry," but 
I shall reply, "Hardly anyone writes poetry." 

/ Every imitative art has its own alphabet of signs, 
and I much wish some man of taste and intelligence 
would make a study of them and compare them. 
The beauties of one poet have oftentimes been com- 
pared with those of another. But one task is still un- 

j' attempted — to collect the beauties of poetry, paint- 
ing and music, and show their analogies with one 
another ; to explain how the poet, the painter and 
the musician will express the same idea ; to seize 
upon their most fleeting images of expression and 
examine the likeness, if there is a likeness, between 
the imagery of the different arts, I should advise 
you to add this as a chapter to your Fine Arts 
reduced to a Single Principle, and I should also like 
you to include, at the beginning of your book, a 
chapter to define in what the beauty of nature con- 



LETTER ON THE DEAF AND DUMB 209 

sists.^ For some people are oi opinion that for lack 
of one of these chapters your treatise is without a 
firm foundation, and for lack of the other of little 
practical use. Tell them, sir, the different methods 
of the arts in treating the samp subject, and 
tell them it is false that nature is only ugly when 
out of place. They ask me why an old gnarled and 
twisted oak, with its branches lopped, and which I 
should have felled if it grew near my door, is just 
the tree a painter would set by my cottage door, if 
he had to paint it? Is the oak beautiful or ugly? 
Which is right — the owner or the painter ? There is 
no subject of imitative art which does not arouse 
this and other difficulties. They also want to know 
why a scene which is admirable in a poem is not at 
all suitable for a painting? In those fine lines of 
Virgil : 

I/ilerea magna misceri murmiire pontum 
Eviissamque hietnem sensit Neptimus, et imis 
Stagfia refiisa vadis ; graviter commolus et alto 
Prospiciens , sumtna placidum caput extulit iinda ; - 

they ask why it is the painter cannot seize the 
striking moment when Neptune raises his head 

' Diderot used to call Balteux' book a headless book, because after 
he had reduced all the fine arts to a single principle — that of imitating 
the beauty of nature, — he never explained what the beauty of nature 
consisted in. — Naigeon, Alemoires. 

2 Meantime the turmoil of the main 

The Tempest loosened from its chain ; 
The waters of the nether deeji 
Upstarting from their trancjuil sleep 
On Neptune broke : disturl)ed he hears, 
And, quickened by a monarch's fears, 
His calm broad brow o'er ocean rears. 

y-EnciJ, lib. i, v. 128 [Irs. Coiiington). 

H 



2IO DIDEROT'S PHILOSOPHICAL WORKS 

above the waves ? Why should the god, who then 
looks like a decapitated man, cut such a poor figure 
on the water, when the effect in the poem was so 
impressive ? Why is it that what appeals to our 
imagination in poetry will not please our eyes when 
painted ? Perhaps there is one beauty of nature for 
the painter and another for the poet ? Heaven knows 
what conclusions they will draw from this theory. 
I hope you will deliver me from these busybodies ; 
meantime, I am going to give you a single example 
of the imitation of one subject in nature by poetry, 
painting and music. 

The subject is a dying woman. The poet will say : 

///(fi, graves oculos conata adiollere, rursus 
Deficit. Infixuffi stridit sub pedore viclnus 
Ter sese adtollens cubitoque adnixa levavit ; 
Ter revoluta toro est oculisqiie errantibus alto 
Qiucsivit avlo iucet/i, ingemuitque reperta ; ^ 
or 

Vita quoque oninis 
Omnibus e nervis atque ossibus exsoivatur.'^ 

The musician will begin by descending a semitone 
{a) : Ilia, graves oculos conata adtollere, rursus deficit ; 
then he will go up a fifth, and after a rest, by the 
still more difficult interval of a tritone {b). 

^ The dull eyes ope, as drowned by sleep, 

Then close ; the death wound gurgles deep. 
Thrice on her arm she raised her head, 
Thrice sank exhausted on the bed. 
Stared with blank gaze aloft, around 
For light, and groaned as light she found. 

\'irgil, ^^neid, lib. iv, v. 688 [Irs. Conington). 

- And life break wholly up out of all the sinews and bones. 

Lucretius, de Reriini Nat., lib. i, vv. 8io, 8ii. 



LETTER ON THE DEAF AND DUMB 211 

Ter sese adtollens will go up a semitone {c) : 
Oculis errantibus alto quccsivit ccelo lucem. This little 
interval will express the ray of light. This is the 



E/Xemple 



l> i- d cL cU^ e. 



C f rr '- lULx:^ ^ 



35 



iJe nic -mcurj,- a nie^f ueux /c/01.^ cejje c/o Lu- re 



*7 ^ 






'■^l^J 'J 



j7 



>C-. yf. i. 




Fig. 8. 



dying woman's last effort. After this she will sink 
by scale {d) : Revoluta toro est. She will expire at 
last, and breathe her last by an interval of a semitone 
Ke) : Vita quoquc omnis omnibus e nervis atqiie ossibus 



2 12 DIDEROT'S PHILOSOPHICAL WORKS 

exsolvatur. Lucretius expresses the dying away of 
her strength by the weight of the two spondees — 
exsolvatur ; and the musician will express it by two 
minims, tied (/) : and the cadence on the second of 
the minims will give a very striking imitation of the 
vacillating motion of a dying lamp. 

Now look at the painter's method of expression, 
and }OU will recognise the exsolvatur of Lucretius 
in the legs, the right arm, and the left hand. The 
painter who can express but a moment in time has 
not been able to represent so many symptoms of 
dissolution as the poet, but they are much more 
affecting ; the painter shows us reality, whereas the 
expressions of the poet and the musician are but 
symbols. When the musician is an artist, the ac- 
companiment either emphasises and strengthens the 
melody, or brings in new ideas which the subject 
demands and which the melody cannot express. 
Thus the first bars of the bass express a gloomy 
harmony, made up by a superfluous chord of the 
seventh, placed as it were outside the ordinary rules 
and followed by another chord, discordant in sound 
and of a diminished fifth {g). The rest will consist 
of a series of minor sixths and thirds (//), which are 
descriptive of exhaustion of strength and prepare 
the mind for its total extinction. 

It is the equivalent of Virgil's spondees : 

Alto qucesivit ccelo lucetn. 

This is but the rough sketch, which I leave for a 
more accomplished hand to complete. 1 make no 



LETTER ON THE DEAF A AW DUMB 213 

doubt that, in this very subject I selected, instances 
could be found in our painters, poets, and musicians 
which would offer more and more striking analogies 
between the different arts. But I leave it to you, 
sir, to look for them and utilise them, for you must 
be painter and poet, philosopher and musician ; for 
you would not have attempted to reduce the fine 
arts to a single principle, if you had not been equally 
well acquainted with them all. 

The poet and the orator gain by studying harmony 
of style, and the musician finds his compositions 
are improved by avoiding certain chords and certain 
intervals, and I praise their efforts ; but at the same 
time I blame that affected refinement which banishes 
from our language a number of vigorous expressions. 
The Greeks and Romans were strangers to this false v 
refinement, and said what they liked in their own 
language, and said it as they liked. By over- 
refining we have impoverished our language ; and 
though there may be only one term which expresses 
an idea, we prefer rather to weaken the idea than 
to express it by some vulgar word or expression. 
How many words are thus lost to our great imagina- 
tive writers, words which we find with pleasure in 
the pages of Amyot and Montaigne ! They were 
at first rejected from a refined style, because they 
were commonly used by the people ; later on they 
were rejected by the common people, who always ape 
their betters, and they are become entirely obsolete. 
I believe we shall soon become like the Chinese, 
and have a different loritten and spoken language. 



214 DIDEROT S PHILOSOPHICAL WORKS 

This, sir, is almost my last observation ; we 
journeyed on together, and I feel it is time to quit 
one another. If I detain you for a moment longer 
as we are leaving this maze in which I have led 
you, it is but to recapitulate in a few words its 
turnings and windings. 
^^ I believed that, in order to clearly understand the 

nature of inversions, we should examine the forma- 
tion of spoken language. 

/ inferred from this exavmiation (i) that our 
language was full of inversions when compared with 
the animal language, or with the first stage of spoken 
language, when it existed without cases, declensions, 
conjugations, and syntax ; (2) that if we have in 
French hardly any of what we call inversion in 
ancient languages, this is perhaps due to modern 
peripateticism, which by realising abstractions gave 
them the place of honour in speech. 

As a consequence of these truths I thought that 
we could, without studying the origin of spoken 
language, obtain results by the study of gesture- 
language alone. 

/ suggested two methods of learning the language 
of gesture — experiments with a "theoretical mute," 
or loner conversations with one born deaf and dumb. 

The idea of a theoretical mute ^ or taking (hypotheti- 
cally) speech from a man, to get a clearer idea of the 
formation of language, has led me to consider man 
as divided into as many distinct and separate entities 
as he has senses ; and I think that if, to form a 
correct judgment of an actor's intonation, we must 



LETTER ON THE DEAF AND DUMB 215 

listen to him without seeing him, it is natural that 
we should look at him without listening to him if 
we are to form a correct opinion of his gestures. 

In reference to energetic gesture-la7iguage , I related 
some striking examples of this, which led me to dis- 
cuss a variety of the sublime which I call siibliiiiity 
of sittiation. 

The order that existed in the gestures of one born 
deaf and dumb (whose informal conversation seemed 
to me more valuable than experimenting with a 
"theoretical mute"), and the difficulty in transmit- 
ting certain ideas to this deaf-mute, led me to dis- 
tinguish in spoken language between those symbols 
which were first introduced and those of later 
introduction. 

/ saw that the symbols which in speech denoted 
indefinite divisions of quantity and time were among 
the last to be introduced, and I realised why some 
languages were without several tenses, and why 
other languages used one tense with two meanings. 

This lack of tenses in one language, and this mis- 
use of tenses in another, led me to distinguish three 
stages in the formation of a language — \\.s primitive, 
Its formative, and Ms perfected s\.K\.e. 

I saw, when language was formed, that men's 
minds were hampered by syntax, and by the im- 
possibility of thinking in the order which reigns in 
Greek and Latin period.s. Hence I concluded ( i ) that, 
whatever the order of words in an ancient or modern 
language, the writer's mind follo\\'ed the order of 
French syntax ; (2) that, as this sj'ntax is the 



2i6 DIDEROTS PHILOSOPHICAL WORKS 

simplest of all, the French language had the advan- 
tage in this and many other respects of the ancient 
languages. 

Moreover, / pj-oved by the introduction and the 
utility of the. article hie and ille in Latin and le in 
French, and by the fact that we have to experience 
several perceptions simultaneously in order to form 
a judgment or make a speech, that when the mind is 
not hampered by Greek and Latin syntax the order 
of its ideas is not dissimilar to our syntax. 

In tracing the transition of language from the 
formative to the perfected state we meet with 
harmony of style. 

L compai-edh^ivraonyoistyXe with musical harmony, 
and / ai)i convinced (i) that the first harmony in 
words was the result of quantit}' and a certain com- 
bination of vowels and consonants, suggested by 
instinct ; and that in sentences it was the result of 
the order of words ; (2) that this periodic and syllabic 
harmony produced a sort of language of symbols 
which is peculiar to poetry ; and I then treated this 
symbolic language, and analysed several passages of 
the greatest poets. 

As a result of this analysis I ventured to maintain 
that it is impossible to translate a poet into another 
language, and that it is an easier thing to understand 
a geometrician than a poet. 

I proved by two examples the difficulty of clearly 
understanding a poet : by the example of Longinus, 
Boileau, and La Motte, who misunderstood a passage 
in Homer ; and by the example of the Abbe de 



LETTER ON THE DEAF AND DUMB 217 

Bernis, who seemed to me to misunderstand a passage 
of Racine. 

After I had defined the date when syllabic 
symbolism was introduced into a language, / 
observed that every imitative art had its own 
language of signs, and that it would be a good 
thing if a man of taste and learning would under- 
take to compare them. 

Here I have hinted that this work is expected of 
you ; and that those of us who have read your Fine 
Arts reduced to the Imitation of Beauty in Nature 
demand that you should define in what beauty in 
nature consists. 

I expect you to compare the language of signs 
in poetr\-, painting, and music ; meantime, I have 
ventured to make some observations of my own upon 
this subject. 

Musical harmony, which was necessaril)' included 
in the discussion, led my thought to the harmony of 
speech. I said that the limitations im]5oscd by each 
were much more sujjportable than an affected refine- 
ment which tends dail)' to impoverish our language ; 
and I emphasised this point until I came to that 
passage where I took leave of you. 

But do not suppose, from my last observation, 
that I withdraw my preference for French above 
all the languages of antiquity and the majority of 
modern languages. This is still my feeling, and 1 
still think that French is superior in utility (if not in 
beauty) to Greek, Latin, Italian and English. 

The objection may be perhaps raised that if, as I 



2i8 D IDE ROTS PHILOSOPHICAL WORKS 

submit, the languages of antiquity and those of our 
neighbours are superior in beauty, we all know that 
these languages do not play us false when we wish 
to treat of ordinary practical matters. 

But I make answer that if our language is admir- 
able for its utility, it can also lend itself to the pur- 
poses of art. There is no role it has not successfully 
assumed. It has been gay and fanciful with Rabelais, 
naive with La Fontaine and Brantome, musical in 
Malherbc and Flechier, sublime in Corneille and 
Bossuet. What an instrument it is in Boileau, in 
Racine, in Voltaire, and in a host of other writers of 
poetry and prose ! Do not let us waste our pity on 
it. If we know how to use it, our works will be as 
precious in the eyes of posterity as the works of 
classical antiquity are in our own. In the hands of 
a commonplace man, Greek, Latin, English and 
Italian will utter only commonplaces, while the pen 
of a man of genius will work miracles with French. 
Whatever language it is written in, a work inspired 
and sustained by genius never falls or flags. 



NOTES 

[Note I. — The specimens of the arithmetic which 
I have perused and reduced to common numbers 
are certain arithmetical tables, which he had 
computed and preserved for his own use ; but for 
what purposes they seem calculated does not easily 
appear. They seem to have some relation to the 
tables of natural sines, tangents, and secants ; but 
their full use I must leave to future inquiry. They 
are four pieces of solid wood, of the form of 
rectangular parallelopipeds, each about eleven 
inches long, five and a half broad, and something 
about half an inch thick. The two opposite faces 
of every one were divided into little squares after 
the manner of the abacus above described, but they 
were perforated only in the necessary places where 
the pins were stuck fast up to the head. Each face 
exhibited nine small arithmetical tables of ten / 
numbers each ; and every number, generally speaking, 
consisted of five places or figures. — " Dr Saunderson's 
Palpable Arithmetic dccyphercd," prefixed to Saun- 
derson's Algebra (1740), pp. xxiii and xxiv.] 

\^Note 2. — A blind man moving in the sphere of 

a mathematician seems a phenomenon difficult to 

be accounted for : Fully mentions it as a thing 

219 



2 20 DIDEROT S PHILOSOPHICAL WORKS 

scarce credible in his own master in philosophy, 
Diodorus, " that he exercised himself in philosophy 
with more assiduity after he became blind ; and, 
what he thought next to impossible to be done 
without sight, that he professed geometry, describ- 
ing his diagrams so expressly that his scholars drew 
every line in its proper directions." 

St Jerome relates a more remarkable circum- 
stance in Didymus of Alexandria, who, "though 
blind from his infancy, and therefore ignorant of the 
very letters, not only learnt logic, but geometry 
also to perfection, which seems the most of an)-- 
thing to require the help of sight. " 

Trithemius, de Scripto)ibiis Eccles., mentions 
Nicaise de Voerde, at Mechlin, " who, though blind 
from the first year of his age, became so eminent 
in learning, that he taught the canon and civil law 
in the university of Cologne, and quoted books 
only from having heard them read to him." I have 
further heard of a Hollander, and some others, 
whom blindness did not hinder from excelling in 
mathematical learning. Indeed, if we consider that 
the ideas of extended quantity, which are the chief 
objects of mathematics, may as well be acquired from 
the senses of feeling as that of sight ; that a firm 
and steady attention is the principal qualification for 
/this study ; and that the blind are necessarily 
<«^more abstracted than others, we shall perhaps 
find reason to think there is no other branch of 
science more adapted to their circumstances. — Life 
of Saunderson, ibid. ] 



NOTES 221 

\^Note 3, — The elephant and tortoise illustration 
had been first introduced by Locke in his criti- 
cism of the idea of substance (Essay concerning 
Human Understanding, bk. ii, ch. 13, § 19, and 
again ch. 23, | 2). It had been further developed 
by his- disciple Shaftesbury {Characteristics: the 
Moralists, vol. ii, p. 15) to criticise the solutions 
given to the problem of the origin of evil. From 
Shaftesbury Diderot appears to have taken both the 
idea and the illustration : in paragraph xxii of his 
Sufficiency of Natural Religion, where he boldly 
applies to the story of Adam the ridicule which 
Shaftesbury seemed to cast on the myth of 
Prometheus only. Why does man suffer in this 
world ? That is a mystery, says the Christian. 
That is a mystery, says the man of science. 
Observe that the Christian's answer is finally re- 
duced to this. If he says : " Man suffers, because 
his forefathers sinned," and you press him with 
" Why should the descendant pay for his forefather's 
folly ? " he replies : " That is a mystery." " Well," 
I should reply to the Christian, "why did you not 
say at first, as I do, that if man suffers in this 
world, ai)parently without deserving it, that is a 
mystery ? Don't you see that your explanation is 
like the Chinese explanation of the suspension of the 
earth in mid air? 'Chinaman, what carries the earth?' 
' A great elephant. ' ' And what carries the elephant?' 
'A tortoise.' 'And what carries the tortoise?' 
' I don't know.'" Ah, my friend, drop the elephant 
and the tortoise and admit your ignorance. 



222 DIDEROPS PHILOSOPHICAL WORKS 

In the above instance Diderot had described the 
elephant and tortoise theory to a " Chinois " ; in the 
Letter on the Blind he reverted to the oricfinal 
"Indian."] 

\^Note 4. — We are ... to consider concerning 
perception, that the ideas we receive by sensation 
are often in grown people altered by the judgment, 
without our taking notice of it. When we set 
before our eyes a round globe, or any uniform 
colour — e.g. gold, alabaster, or jet, — 'tis certain that 
the idea thereby imprinted in our mind is of a flat 
circle variously shadowed, with several degrees of 
light and brightness coming to our eyes. But we 
have by use been accustomed to perceive what kind 
of appearance convex bodies are wont to make on 
us ; what alterations are made in the reflections 
of light, by the difference of the sensible figures 
of bodies ; the judgment presently, by an habitual 
custom, alters the appearances into their causes, so 
that from that, which truly is variety of shadow or 
colour, collecting the figure, it makes it pass for a 
mark of figure, and frames to itself the perception 
of a convex figure, and an uniform colour ; when the 
idea we receive from thence is only a plane variously 
coloured ; as is evident in painting. To which 
purpose I shall here insert a problem of that very 
ingenious and studious promoter of real knowledge, 
the learned and worthy Mr Alolineux, which he was 
pleased to send me in a letter some months since, and 
it is this : 



NOTES 223 

" Suppose a man born blind, and noiv adult, and 
taugJit by his touch to distinguish between a cube 
and a sphere of the same metal and nighly of the 
same bigness, so as to tell, wJien he felt one and 
t'other, ivJiich is the cube, ivhich is the sphere. 
Suppose then the cube and sphere placed on a table, 
and the blind man to be made to see : QucBre, whether 
by his sight before he touched them, he could now 
distinguish, and tell, which is the globe, ivhich is the 
cube. To which the acute and judicious proposer 
answers, Not. For though he has obtained the ex- 
perience of J low a globe, how a cube affects his touch, 
yet he has not yet attained the experience, that what 
affects Ids touch so or so, must affect his sight so or 
so. Or that a protuberant angle in the ctcbe, that 
pressed his hatid unequally , shall appear to his eye 
as it does in the cube. I agree with the thinking 
gentleman whom I am proud to call my friend, in 
his answer to this his problem ; and am of opinion, 
that the blind man, at first sight, would not be able 
with certainty to say, which was the globe, which 
was the cube, whilst he only saw them ; though he 
could unerringly name them by his touch, and 
certainly distinguish them by the difference of their 
figures felt. " — An Essay concerning Human Under- 
standing, vol. i, pp. 107, 108 (ed. 172 1).] 

l^Note 5. — Condillac, I'^tienne Bonnot de (17 15- 
l^So), 3 French philosopher, was born at Grenoble, 
and took orders and became the Abbe de Mureau. 
The profession was nominal, and Condillac's whole 



\ 



224 DIDEROTS PHILOSOPHICAL WORKS 

life was devoted to speculation. His works are : an 
Essay on the Origin of Human Knou'ledge {\y 4.6), 
the Preatise on Systems (1798), Preatise ott Sensa- 
tions {'^7^7-'^77Z)} i" fifteen volumes, and two post- 
humous works — Logic {\72)\), and the Language of 
Calculation (1798). In his earlier days in Paris he 
came much into contact w^ith the circle of Diderot. 
He spent his later years in retirement at a property 
he had bought near Beaugency, and died there on 
August 3rd, 1780. Condillac is important as a 
ps>'chologist, and as having established systematic- 
all}' in France the principles of Locke, whom Vol- 
taire had lately made fashionable. In his Preatise 
on Sensations he questions Locke's doctrine that the 
senses give us an intuitive knowledge of objects, 
and that the eye judges naturally of shapes, sizes, 
positions, and distances. 

The plan of Condillac's book is the idea of a 
statue organised like a man, with a soul which has 
never received an idea, into which no sense-impres- 
sion has ever penetrated. He then treats of the 
senses one by one, beginning with smell. As an 
example of his careful and detailed treatment, the 
headings of some of the chapters may be quoted : 
"Of the Ideas of a Man limited to the Sense of 
Smell" ; "Of a Man limited to the Sense of Hearing"; 
"Of Smell and Hearing Combined"; " Of Taste 
by Itself, and of Taste Combined with Smell and 
Hearing '' ; " Of a Man limited to the Sense of Sight. " 
In the second section of the treatise the statue is 
invested \\ ith the sense of touch which first informs 



NOTES 225 

him of the existence of external objects. " Apart 
from any definite propositions, Condillac did a 
notable work in the direction of making psychology 
a science : it is a great step from the desultory, 
general observation of Locke to the rigorous analysis 
of Condillac, short-sighted and defective as that 
analysis may seem to us in the light of fuller 
knowledge. " ^] 

\Note6. — William Cheselden (1688- 175 2), a well- 
known surgeon and anatomist. In 1728 he wrote 
a paper {Phil. Trans., xxxv, 447) entitled "An 
account of some observations made by a young 
gentleman who was born blind . . . and was couch'd 
between thirteen and fourteen years of age." The 
account of this youth's experience is clear and 
masterly, but brief, and most students have regretted 
that the opportunity was not seized for more detailed 
observations. See also Voltaire, Elemens de la 
philosophie de Newton, pt. ii, ch. vii {CEuvres com- 
pletes, ed. Beuchot, t. i, 1879, pp. 469, /j70), where 
Voltaire summarises the case.] 

' Art. "Condillac," Encyclopedia Britaniiica, vol. vi, pp. S49-851 
(nth edition). 



IS 



APPENDIX 
BLINDNESS 

From the Encyclopcedia of Diderot and d'Alembert, 
vol. i, p. 870. The translation is that which appeared 
in Select Essays from the Encyclopedy, pp. 132-147, 
London (1782), in which it is attributed to d'Alem- 
bert. The translation has been revised and corrected. 
In the translation, two passages which were omitted 
have been inserted, i.e. the sentence, " If we except 
certain passages which are not immediately connected 
with the subject and may offend pious ears," and the 
paragraphs, "Imagine a square " to "Philosophers 
and beginners would have found it useful." 



BLINDNESS 

One may be born blind, or become so through acci- 
dent or malady. It is not our intention here to 
treat either of the diseases of the eye, or of other 
accidents that may occasion a loss of sight. We 
shall confine ourselves to make philosophical reflexions 

upon blindness, through the ideas of which we are 

226 



APPENDIX 227 

deprived by it as well as through the advantage 
acquired by the other senses in consequence of it. 

From the known truth of the sense of seeing being 
more fitted to distract us by the diversified qualities 
of objects which it presents to us at once, it follows 
that they who are deprived of this faculty must 
naturally, for the most part, apply with a closer 
attention to the objects which fall under their other 
senses. And this is the principal reason of that 
delicacy of touch and hearing that has been observed 
in some blind people, which is by no means the effect 
of a real superiority in these two senses ; whereby 
nature means, as it were, to compensate in some 
sort for their loss of sight. 

So true is this position, that a person become blind 
through accident finds often in the succour of the 
other senses a resource which he knew not of before ; 
and this is to be ascribed solely to that person's being 
less distracted and become more capable of attention. 
But it is chiefly in persons born blind that we are to 
remark (if such an expression may be allowed) the 
miracles of blindness. 

An anonymous author published in the year 1749 
a little philosophical work, very elegantly written, 
and entitled. Letter on Blindness for the use of those 
who can see ; with this motto : 

" Possunt quia posse videntiir," 

which alludes to the prodigies that iiave been observed 
in folks born blind. We purpose to give in this 
article an extract of that ingenious work, whose 



228 DIDEROT S PHILOSOPHICAL WORKS 

metaphysical reasoning, though very subtle, is yet 
true in general, if we except certain passages which 
are not immediately connected with the subject and 
which may be offensive to pious ears,^ 

The author sets out by making mention of a 
person born blind with whom he was acquainted, 
and who is probably still alive. This extraordinary 
man, who lived at Puisaux in Gatinais, was both 
chemist and musician. He taught his son to read 
with characters in relievo. He could judge with 
exactness of symmetry. But it is very likely that 
the idea of symmetry, which is with us in many 
respects but a matter of mere convention or agree- 
ment, is still more so to him. The definition which 
he gives of a looking-glass has something very 
singular. "It is," according to him, "a machine, 
by means whereof things are exhibited in relievo 
out of themselves." This definition indeed may 
appear absurd to a blockhead who has eyes ; but 
a true philosopher, however keen-sighted, will pro- 
nounce it to be no less subtle than surprising. " Had 
Descartes been born blind," says our author, " he 
might be proud of it." By what a delicate train of 
ideas must he have been led so far ! Our blind man 
could have, in this affair, no knowledge but through 
the medium of his feehng. He conceived, from 
what he had heard other men relate to him, that 
it is by the faculty of sight they come to a know- 
ledge of objects, as in a kindred manner he does by 
the mediation of feeling : it was the only notion he 

' " If we except . . . ears " omitted in the original translation. 



APPENDIX 229 

could form to himself. He had learned, moreover, 
that a man cannot see his face, though he can touch 
it. Sight then, in his sense, must have been a 
species of feeling or touching, that extends itself 
to any proper objects that are different from our 
countenance and placed at a distance from it. Be- 
sides, the sense of touching or feeling in this case 
excited in him the idea of a relievo. Therefore, 
adds he, "a looking-glass is a machine that places 
us in relievo out of ourselves." Let it be observed, 
that the words in relievo are by no means redundant 
here; for, had the blind man simply said, "which 
places us out of ourselves," it would have been an 
absurdity ; because how can we conceive an object 
that is to double itself? The words i7i relievo here 
are only applied to the surface ; wherefore by " our- 
selves being placed iti relievo out of ourselves," 
nothing more is meant than the representation of 
the surface of our bodies being made out of our- 
selves. 

The blind man must have been induced by his 
manner of reasoning to think that feeling represents 
to him only the surface of bodies, and that therefore 
the species of touching or feeling called sight gives 
us but an idea of the relievo, or the surface of bodies, 
without giving that of their solidity ; the words in 
relievo here meaning no more than surface. 

I own here that the blind man's attempt at an 
explanation, notwithstanding this restriction, is an 
enigma to him ; but a pleasure that must hence 
result to all reflecting minds is to observe (consider- 



230 DIDEROT S PHILOSOPHICAL WORKS 

ing his situation) the very ingenious method employed 
by him to diminish, and, as far as by him practicable, 
to solve the enigma. 

It must strike everybody that mirrors, and every 
kind of glasses which enlarge, diminish, or multiply 
objects, were impenetrable mysteries to him. " He 
asked if the glass that increased objects was 
shorter than that which lessened them ; or if that 
which drew them near was less than that which 
threw them off at a distance ; and not being able to 
conceive how the other ourselves were impalpable to 
feeling, he cried out, " I perceive that two senses are 
put in contradiction to one another by the means of 
a little machine ; another, more perfect, would make 
them agree ; and a third, still more perfect and less 
perfidious, would make all those phantoms disappear 
and convince us that we had been in error." What 
philosophical conclusions might not a person born 
blind be enabled to bring against the fallacy of our 
senses ! 

He defines the eyes to be an organ on which the 
air causes the same effect as a stick upon the hand. 
The author we abstract from here observes that this 
definition has some resemblance with that of 
Descartes, who in his Dioptrics compares the eye 
to a blind man that touches objects at a distance 
with his stick. The rays of light are the sticks of 
the clear-sighted. 

Our bUnd man's memory of sounds is to a most 
amazing degree ; and he distinguishes among the 
variety of voices with as much accuracy and quick- 



APPENDIX 231 

ness as those who see can among that of faces. 
The succour which he derives from his other senses, 
and the very surprising use which he makes thereof, 
to the astonishment of all whom he has any concern 
with, render him almost indifferent about the loss of 
sight. He is sensible enough that in some circum- 
stances he has advantages over those who can see ; 
which make him, instead of being desirous of sight, 
to wish, as an equivalent thereto, for longer arms. 

He addresses himself directly towards the place 
\vhence any noise or voice affects his ear. He 
judges of the proximity of fire by the degree of heat ; 
of the plenitude of vessels by the noise which 
liquors make as they are poured from them ; of the 
nearness of bodies by the action of the air upon his 
face : he can distinguish an open street from a cul- 
de-sac (one that has no passage through it) ; which 
proves that the air, relatively to him, is never in an 
absolute state of rest, and that his countenance is 
instinctively sensible of the least vicissitude in the 
atmosphere. 

He judges wonderfull}' well of the weight of 
bodies and the capacity of vessels ; he has trained 
his arms to serve him as exact scales or balances, 
and his fingers as compasses that never deceive him. 
The smoothness of bodies has as many variations for 
him as the sounds of the voice. He judges of beauty 
by the touch ; and, what is singular, he makes the 
sound of the person's voice, with their manner of 
pronouncing, come in for a share of this judgment. 

He executes several little works in the turning 



232 DIDEROTS PHILOSOPHICAL WORKS 

way and with a needle ; he takes a level with a 
square ; he puts together or takes asunder pieces of 
common machinery ; he performs pieces of music, 
the notes and their value being first told him ; he 
estimates, with much more precision than we do, 
the progress of time, and that by the succession of 
actions and thoughts. 

He has an implacable hatred of thieves ; and the 
reason, no doubt, arises from the difficulty, or rather 
impossibility, in which he is to perceive when he 
is robbed ; he has but little, or rather scarce any, 
notion of what modesty consists in ; he looks upon 
clothes as necessary for protecting our bodies from 
the injuries of the air, but he cannot comprehend 
why certain parts of the body should be covered 
preferably to others. " Wherefore," says the author 
we abridge from, " Diogenes would not have ranked 
as a philosopher in the opinion of our blind hero." 
In fine, the exterior appearance of worldly pomp, 
with which the generality of mankind are so much 
affected, impose not upon him in the least, which 
in the kingdom of reason is no despicable article." 

We pass over in silence a great number of very 
subtle and refined reflections made by the author we 
quote from upon the French blind man, to proceed 
to what he says of another celebrated personage in 
the same situation ; and that is the famous Saunderson 
of England, a professor of mathematics at Cambridge, 
who died a few years ago. 

When an infant, he lost his sight by the small-pox, 
and so early that he did not remember to have ever 



APPENDIX 233 

seen. He had no more ideas of light than a person 
born blind. Notwithstanding his misfortune, he 
made such a surprising progress in the mathematics 
that the professorship thereof was conferred on him by 
the above-mentioned University. His lectures were 
exceedingly clear ; and the reason assigned for it is, 
that he used to address himself to his pupils as if 
they were all deprived of sight : whence it followed, 
of course, that the blind teacher who could explain 
his meaning clearly to blind pupils must have a 
great advantage with those who could see, from 
their quickness of conceiving him. He taught his 
scholars the calculations he had made. 

Imagine a wooden square divided by perpendicular 
lines into four small squares ; suppose this square 
pierced with nine holes capable of receiving pins of 
the same length and thickness, but of which some 
had larger heads than others. 

Saunderson had a great number of these little 
squares traced on a large board. To denote the 
cipher nought, he would place a large-headed pin in 
the centre of one of these squares, and no pin in the 
other holes. To denote the number i, he placed a 
small-headed pin in the centre of a little square. 
To denote the number 2, he placed a large- headed 
pin in the centre, and above, in the same line, a 
small pin in the corresponding hole. To denote 3, 
a large-headed pin in the centre, a small-headed pin 
in the centre, and a small-headed pin in a hole 
above to the right ; and so on. Thus Saunderson, 
when touching a small square, perceived at once the 



234 DIDEROT'S PHILOSOPHICAL WORKS 

number it denoted, and on glancing at the following 
table we shall see his method of addition by means 
of these small squares : 



I 


2 


3 


4 


5 


2 


3 


4 


5 


6 


3 


4 


5 


6 


7 


4 


5 


6 


7 


8 


5 


6 


7 


8 


9 


6 


7 


8 


9 


o 


7 


8 


9 


o 


I 


8 


9 


o 


I 


o 


9 


o 


I 


2 


3 



Running his fingers down each vertical row of 
figures from top to bottom, he added up in the 
ordinary manner, and marked the sum by means of 
pins placed in squares at the foot of the above 
numbers. The same board divided into squares 
served for geometrical demonstrations. He placed 
large-headed pins in the holes in the direction of a 
straight line, thus forming polygons, etc. 

Saunderson also left some instruments %vhich were 
of use to him in his study of geometry, but how he 
used them is not known. 

He published his Elements of Algebra, equal to 
the best that has been published on this subject, 
but, as our author observes, elements of his geometry 
would have been even more interesting. I have 
heard from a person of his acquaintance that the 
demonstrations of the properties of solid bodies. 



AP'PENDIX 235 

which are usually a matter of considerable difficulty, 
were child's play to him. His mind moved in a 
pyramid, an icosahedron, from one angle to another, 
with the greatest ease ; he imagined planes and sec- 
tions in these solids without any effort. Perhaps for 
this reason the demonstrations which he might have 
given would have proved more difficult than those of 
a clear-sighted geometrician ; but his demonstra- 
tions on plane geometry would in all probability be 
extremely clear, and perhaps singular. Philosophers 
and beginners would have profited by them. 

Although it may appear very singular to the many 
that he gave lectures upon optics, yet to philo- 
sophical minds the miraculous of this affair dis- 
appears, on reflecting that a blind man, without any 
idea of light or colours, may give lectures upon 
optics, in proceeding like the geometricians who 
look upon the rays of light as straight lines that 
ought to be disposed of and arranged according 
to certain laws in order to cause the phenomenon 
of vision, as well as those observable in mirrors, 
optic glasses, etc. 

Saunderson in running his hand over a series of 
medals could distinguish the false from the true, 
even when they were so well counterfeited as even 
to deceive the practised eye of a connoisseur ; he 
could judge of the exactness of mathematical instru- 
ments by running his fingers over the divisions. He 
was, like the before-mentioned blind man, sensible 
of the least vicissitudes in the atmosphere ; and he 
perceived (in calm weather especially) the presence 



236 DIDEROT S PHILOSOPHICAL WORKS 

of objects near him. As he sat one day in his 
garden meditating on astronomical observations, he 
distinguished, by the impression of the air on his 
countenance, the different times when the sun was 
covered with clouds and when it was not ; which 
is so much the 'more extraordinary, as that he was 
deprived not only of sight but of the organ. 

The pretended history of Saunderson's last mo- 
ments, printed in England, is an absolute imposi- 
tion ; which, though held by many learned men to 
be highly criminal against the majesty of science, 
might be deemed only a stroke of mere pleasantry 
were it not occasioned by so solemn and respectable 
a subject. 

Our author afterwards treats in a cursory manner 
of several other blind personages who in spite of the 
loss of one sense have made a wonderful progress 
in the arts and sciences. He farther observes, and 
not improbably, that the famous Tiresias, who is 
said to have become blind because he had penetrated 
into the secrets of the gods and could predict future 
events, was in all likelihood some celebrated blind 
philosopher, whose name fabulous history hath 
transmitted down to us. Perhaps he was the most 
renowned philosopher of his time, because he could 
foretell eclipses (which to an ignorant people must 
appear astonishing). His becoming blind towards the 
latter end of his life was doubtless occasioned by too 
continued an application that over-fatigued his eyes in 
making such a variety of nice observations, as hath 
since indeed been the case with Galileo and Cassini. 



APPENDIX 237 

There have been many instances of people born 
blind being restored to sight ; as, for example, that 
young lad, about thirteen years old, whom Mr 
Cheselden, a celebrated surgeon at London, re- 
lieved from the cataract that had rendered him 
blind from his birth. This great operator curiously 
observed the progressive manner of his beginning 
to see, which he published in No. 42 of the Philo- 
sophical Transactions, and in the fifty-fifth number of 
the Taller, with his remarks thereon. Here follows 
an extract of those remarks from the third volume 
of Natural History, by Messieurs de Buffon and 
d'Aubenton : 

" This youth, notwithstanding his blindness, could 
distinguish the day from the night, as can all those 
who are blinded by cataract. He could distinguish 
any strong light, as he could also the colours black, 
white, and scarlet ; but he could not discern the form 
of bodies. The operation was first made upon one 
eye. |As soon as the young patient began to see, all 
the objects before him seemed to him as if they were 
applied to his eyes ; and those that appeared the 
more pleasing to him, although he could give no 
reason for it, were such as had a regular form. He 
did not, however, know the colours, which, while 
blind, he could distinguish by the aid of a strong 
light. He could not discriminate one object from 
another, however different the forms were. When 
the objects, which he had known before by feeling, 
were presented to him, he considered attentively 
in order to recognise them ; but, all of a sudden, a 



238 DIDEROTS PHILOSOPHICAL WORKS 

general act of oblivion followed from the multi- 
tude of things that crowded in upon him for 
admiration. 

" He was much surprised in not finding those 
persons handsomer whom he had loved more than 
others. He was a long time before he could be 
made to comprehend how pictures represented solid 
bodies. He at first looked upon them as planes 
differently coloured ; but when he was undeceived, 
and on applying his hands to them, discovered 
nothing beside surface, he asked whether it was the 
sight or the touch which had deceived him. He 
expressed great surprise that in a little space the 
picture of an object much larger than the space could 
be contained ; as, for example, the human counten- 
ance in a miniature portrait, which appeared to 
him equally impossible as to make a quart contain 
a bushel. 

*' At first he could bear but a very small quantity 
of light, and saw all objects very large ; but by 
degrees the first seen looked smaller, as he accus- 
tomed himself to see larger. Although he very 
well knew the chamber in which he was to be of 
less dimensions than the house, yet he could not 
conceive why the house should appear larger than 
the chamber. 

"Before the restitution of his sight, he was but 
very little anxious about the recovery of this addi- 
tional sense to him, because he knew not the loss of it, 
and was conscious of himself that in some articles he 
enjoyed peculiar advantages unknown to others who 



APPENDIX 239 

could see. But as soon as he came to view objects 
distinctly, then he felt real transports of joy. 

" About a year after the first operation, the second 
was performed upon the other eye, and was crowned 
with equal success. He saw at first, with this 
second eye, the objects much larger than they 
appeared to the other ; but, however, not so large 
as they had appeared at first to it, after the opera- 
tion a year before. When he looked steadfastly on 
an object with both his eyes, he said that the object 
appeared to him as big again as when he looked at 
it oiily with his first eye. " 

Mr Cheselden mentions several others born blind, 
whom he had freed from the cataract, and observed 
in them the same phenomena, without entering into a 
like detail. He remarks that from their not having 
been used to move their eyes during the state of blind- 
ness, it was but by degrees that they learned how 
to direct them towards objects. 

From the result of these experiments it must 
clearly appear that the sense of seeing arrives at 
perfection but by slow degrees, and is at first very 
confused ; and that we learn to see, pretty nearly 
as we learn to speak. A new-born babe, that opens 
its eyes for the first time to the light, feels, no 
doubt, the same progressive emotions which have 
been observed in the lad born blind. By the agency 
of feeling and custom the erroneous judgments of 
infant sight are corrected gradually. 

Let us now return to our author, who says : " We 
seek for people born blind, in order to examine 



240 DIDEROT S PHILOSOPHICAL WORKS 

through them how vision is formed ; but I beHeve," 
adds he, "that we may equally profit by putting 
questions to any other bhnd person of good sense ; 
and, that some certainty might result from such 
experiments, the person, by whose means they are 
to be made, should for the purpose be prepared a 
long time beforehand, and perhaps rendered some- 
what philosophical. It would not also be amiss to 
defer beginning the observations until a long time 
after the operation shall have been made. For this 
purpose, it would be proper to treat the patient in 
the dark, and to be assured that the wound were quite 
sound, as also that the eyes are sound ; nor ought 
he to be at first, or too soon, exposed to broad day. 
An attempt of this kind, from the delicacy of its 
nature, would be attended with difficulties, lest a 
subject thus prepared should balk our expectations, 
and, though most cautiously interrogated, might not 
inform us exactly how things pass within him. 
Besides, the most learned and the most polished 
members of society are not too good to participate 
in such nice and philosophical experiments." 

Let us put an end to this article, with the author 
of the LetteVy with the famous question of Molyneux, 
who supposes that a person born blind has learned, 
by the touch or feeling, to distinguish a globe from 
a cube, then asks, if, when sight shall be restored 
to him, he will immediately distinguish the globe 
from the cube without touching them. Molyneux 
believes not ; and Mr Locke is of his opinion ; because 
the person born blind cannot know that the advanced 



APPENDIX 241 

angle of a cube, which presses on his hand in an 
irregular manner, is to appear to his eyes what it 
appears in the cube. 

Our above-quoted author, who founds his opinion 
on Cheselden's experiment, inclines to believe (and 
with reason) that a person born blind must at first 
see all objects in a very confused manner, and that, 
so far from distinguishing the globe from the cube, 
he will not have a distinct perception of the two 
different figures. He believes, however, that in the 
long run, and without the assistance of touching, 
the new spectator will learn to make a distinction 
between the two figures. The reason which he 
alleges, and that cannot be easily refuted, is that, 
the blind person not being necessitated to employ 
his touch to distinguish colours one from another, 
the limits of colours will at length suffice to teach 
him how to discriminate the form and the contour ot 
different objects. In fine, he will see a globe and a 
cube ; that is, a circle and a square. But the tact, 
or sense of touching, having no relation whatever to 
that of sight, he will not be able to guess that one 
of those bodies is what he calls a globe and the 
other a cube : so vision will by no means recall to 
his memory a sensation which he had received by 
the tact. Let us now suppose him to be told that 
one of these two bodies is what by tact he felt to 
be a globe, and the other a cube : will he be able 
to distinguish them ? The answer given by our 
ingenious author is, that an uninstructed and grossly 
ignorant person would hastily pronounce at all 

16 



242 DIDEROT S PHILOSOPHICAL WORKS 

events ; but that a metaphysical or geometrical 
mind, such as Saunderson's, would proceed with a 
cautious examination of those figures ; and when, 
by the supposition of certain lines therein, he would 
find that he can demonstrate in the one all the 
properties of the circle which he had learned by 
the tact, and in the other all those of a square, he 
would immediately be tempted to pronounce, " That 
is the globe, and this is the square." However, if 
he be prudent, he will be dubious of giving so pre- 
cipitate a judgment, and thus reflect within himself: 
" Perhaps, on an application of my hand to these 
two figures, they will be mutuall}' transformed one 
into the other, so that the first figure might serve 
for my demonstrating the properties of a circle 
to blind folk ; and those of a square, to such as 
can see." 

But a Saunderson would reply in the negative : 
" I am in error: they to whom I demonstrated the 
properties of a circle and a square, in whom the 
faculties of seeing and hearing perfectly agreed, 
understood me very well, although they did not 
touch the figures upon which I made the demon- 
stration : they were satisfied with seeing them. 
They did not see a square when I felt a cube : no ; 
for if they had, we should never have understood 
each other. But since they all understood me, it 
is clear that all men see alike. Therefore I see a 
square what they saw a square and I felt to be a 
.square ; and by a parity of reason, I see a circle 
what I felt to be a circle." 



APPENDIX 243 

We have here, in complaisance to our quoted 
author, substituted circle to globe, and square to 
cube ; because there is much reason to believe that 
he who makes use of his eyes for the first time sees 
nothing but surfaces, and knows not what projection 
is ; for the projection of a body consists in some of 
its points being more advanced towards us than 
others. It is then by experience jointly with the 
tact, and not the sight alone, that we are enabled to 
judge of distances. 

From all that has been said of the globe and the 
cube, or of the circle and the square, let us conclude 
with our author, that there are circumstances where 
the reasoning and experience of others furnish a 
new perspicuity to the faculty of seeing through 
its relationship with the tact, and give assurance 
to the eyes that they are in perfect harmony with 
each other. 

The letter-writer concludes with some reflexions 
on what might be the case of a person who should 
have seen from his birth, but was deprived of tact 
or feeling ; and of another, in whom the senses of 
feeling and seeing should be in a perpetual contra- 
diction with each other. But in order to avoid pro- 
lixity here, we refer our readers to his reflexions ; 
but which recall to our memory another, made by 
him in the middle of his work, and of the same 
tendency, viz. : " If a person," says he, "who had 
seen but for a day or two, were to find himself in the 
midst of a blind people, he must take the resolution 
either of holding his tongue, or of passing for a fool ; 



244 DIDEROTS PHILOSOPHICAL WORKS 

because every day he would think he was communi- 
cating some new mystery, and such only to them, 
but which their choice spirits would treat with 
contempt. The advocates for, and defenders of, 
religion might perhaps derive some advantages from 
their cause from an incredulity so obstinate and so 
ill-grounded." 

With this reflexion we close the present article ; 
and it is sufficient to counterbalance several others, 
scattered throughout the work, that indeed seem to 
border on infidelity. 



INDEX 



Algebra (see Elements of Algebra). 
Article, the origin of the definite, 

182-184, 216. 
Augustine, St., 60. 
Aveugle (article in the Etuyclo- 

pizdia), 13, 226-244. 

Batteux, Charles, Abbe, 23, 209 

note. 
Berkeley, George, Bishop of 

Cloyne, 104. 
Bemis, Fran9ois Joachim de 

Pierre de, Abbe, 205-207, 

216. 
Bible, tne authenticity of, 52-53. 
Buffon, George Louis Leclerc, 

Comte de, 2, 237. 

Calculating machines, Saunder- 
son's, 90-99, 219, 233- 

234- 
Castel, Father, his ocular music, 

170-172. 
Characteristics, 22 1 . 
Chesclden, William, 7, 125, 132, 

225, 237, 239, 241. 
Cicero, 55-56, 67, 1S0-182. 
Clarke, Samuel, no. 
Condiliac, Etienne Bonnot de, 7, 

24-25, 104-105, 1 19-120, 
;^ 122, 126, 133, 223-225. 

ufAlemliert, Jean le Rond, 3, 5, 

137, 226. 
d AUmberC s Dream, 4. 
Darwin, Erasmus, I. 
Uaviel, Jacques, 144-145. 
Deaf and dumb alphabet, 8-9, 

89-90. 
de Puisieux (^see Puisieux, Madame 

de). 



de Reaumur {see Reaumur). 

de Salignac {see Salignac, Melanie 

de). 
Descartes, Rene, 34, 64, 73, 102, 

203. 
Design, argument from, 5-6, 10- 

15, 36-39, 109-114- 
de Vandeul {see Vandeul, Madame 

de). 
Diderot, Denis, life of, I-4. 
English influence on, 2. 
works, 2-4. 
Didymus of Alexandria. 108, 

220. 
Dioptrics, 73. 

Elements of Algebra, 8, 16, 17, 
99, 104, 106, 234. 

Elements of the Philosophy of 
Newton, 7, 225. 

Eticyclopivdia, 3, 6, 23, 226. 

Essay concerning Hitman Under- 
standing, 222-223. 

Essay on Merit and Virtue (see 
Ini/niiy concerning Virtue 
and Mei-it). 

Essay on the Origin of Human 
K'noivledge, 7, 104-105, 

119, 122, 126, 224. 

Eusebius the Asiatic, 108. 

Fine Arts reduced to a Single 
Principle, 23, 158, 208. 

French language, 190- 191, 217- 
218. 

Galileo, 102. 

Gesture-language, 25, 163-167, 

175. 214- 
Gregory the Great, 52. 



245 



246 DIDEROT S PHILOSOPHICAL WORKS 



Harmony in music, 217. 
Harmony of style, 192-193. 
Hebrew language, 203-204 
Holmes, Gervase, 10, iIi-19, 

108-114. 
Homer, 199-203. 

Inchlif, William, 115-116. 
Indiscreel Jezue/s, 2, 20, 23. 
Inquiry concerning Virtue and 

Merit, 2, 19. 
Inversion, in language, 160-163, 

176, 178, 180-182, 189- 

192. 

Julian, edict of the Emperor, 50- 
52. 

Lamarck, Jean Baptiste Pierre 
Antoine de Monet, Cheva- 
lier de, 1-2. 

Language, development of, 215- 
216. 

Leibniz, Gottfried Wilhelm, iio- 
III. 

Le Sage, 174-175. 

Letter of Mr Ger 7iase Holmes to the 
Author of the Letter on the 
Blind, 19. 

Letter on the Blind ^ 2-3, 6-1 5, 
20, 23-24, 68-141, 158, 
227. 

Letter on the Blind, Addition to, 

142-157 
Letter on the Deaf and Dumb, 3, 

23-25, 160-218. 
Lifeof Saunderson, by Dr Inchlif, 

10, 115-116. 
Locke, John, 9, 64, 119-120, 221, 

224-225. 
Longinus. 201-202, 216. 

Memoirs of the Life and Character 
of Dr Nicholas Saunderson 
(in Saunderson's Algebra"), 
16-17. 

Method of Fluxions applied to a 
Select Number of Useful 
Problems, 17. 

Miracles, 53-62. 



Molyneux, problem of, 1 18-143^ 

222-223, 240-243. 
Montaigne, Michel de, 41-43, 64, 

140. 
Montgeron, Corre de, 60-62. 
Muet de convention (theoretical 

mute), 24-25, 163-166, 

214-215. 

Natural History, 237. 

Newton, Isaac, 7. 15, 34, 102, 

IIO-III. 

Nicaise of Mechlin, 108, 220. 

Pascal, Blaise, 32. 

Philosophic Thoughts, 3, 4-6, 20, 

27-67. 
Puisaux, the blind man of, 8, 69- 

81, 228-232. 
Puisieux, Madame de, 6-7, 19-20. 

Racine, Jean, 205-206. 
Reaumur, Rene Antoine F"er- 

chault, Seigneur de, 7, 20, 

68-69, 137- 

Saint-Hilaire, Geoflfroy, i. 
Salignac, Melanie de, 146-157. 
Saunderson, Dr Nicholas, 7-8, 

10, 13, 15-19, 90-116, 

137-138, 232-236. 
Sceptic's IValk, The, 3, 6. 
Select Parts of Professor Sauntier- 

son's Elements of Algebra, 

17- 

Shaftesbury, Earl of, 221. 
Symbolism in poetry, 195-200, 
208. 

Thoughts on the Interpretation of 
Nature, 4, 12-13. /W' 

Transformism, i, 11-13, iii-ll^r^ 

Treatise on the Sensations, 24-2^, 
224-225. 

Treatise on Systems, 105, 119, 
132, 224. 

Vandeul, Madame de, 20. 
Virgil, 197-199- . 
Voltaire, Francois-Marie Arouet, 
7, 14, 225. 







BINDING SECT. JAN 4 1972 



B Diderot, Denis 

2012 ^ Early philosophical works 

E5J6 

1916 



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